Cross-Ref of Book in Series or Book - Citing child should makes both child and parent appear in bibliography

Question

Following my success with thesis, I'm getting now to a more complex topic, meaning the cross-referencing.

I got some big law books, called commentaire in french, which containing several sub-parts containing very detailled analysis on some piece of legislation called "article" in french (but this has nothing to do with article entry type). The relation is that the sub-parts (child) are cited in the text, but not the main book (parent). However, both the parent and the child entry should be cited.

I found the settings mincrossrefs which I've set to 1 to trigger the display of both parent and children.

So I've created a new type called "collectif", would contains only the parents infos. This is because these kind of parents type have unique formatting (see below, about authors/editors).

Now, I got some issue, because the formating of both piece should follow very strict rules. I'll start with the parent entry, where my code (MWE below) is mainly working as expected :

1. All the editors should be in standard format (OK)
2. After the names a string "(édit. ) should be displayed
3. After editors, the should be a seperator (OK)
4. The title should be in italic (OK)
5. Finally, there should be a block location + year (OK).

Now the child entry should be similar as what I need in a book. So I've taken the codes from another question I asked. But I've got some issues when attempting to use it. Here are my requirements :

6. Authors is small caps (OK)
7. Title in Italic, not OK, I dont why the style is reset
8. insertion of the cross-ref, the format should be "in :". At the moment I got "in : sous la dir. de "
9. Again, the editors names are in small caps. Not that if a book contains both editors and authors, the authors should nevertheless be in small caps. So I need to have no-small caps only in the parent
10. There is a ", " between the location and the year.

Finally, the addition of my new entry type seems to conflict with previous version : 11. The cited as is broker. It should identify that the "author" of child can also have a duplicate with other bilbiography entries, as in my MWE, there are 3 books/parts of commentaire from author "Bohnet".

At this point, I've tried, but there are too many movings parts and I cannot try to apply the solution proposed in some other questions

Question:

1. What would the fixes of my horrible code be ?

MWE code

Main.tex

% MweBiblatex Swiss Legal
\documentclass{article}

% Needed by Biblatex
\usepackage{polyglossia}
\setmainlanguage{french}
\usepackage{parskip}
\usepackage{csquotes}
\usepackage[style=biblatex-xawi, language=french, bibencoding=UTF8, backend=biber]{biblatex}

\addbibresource{main.bib}

\begin{document}
\section{Test de la bibliographie}
\printbibliography
\section{Tests de citation}

\subsection{Libre}
% Bohnet, livre Procédure : \cite{bohnetLivre} \\
Bohnet, livre Procédure en schéma : \cite{bohnetSchema} \\

\subsection{Commentaires}
Bohnet, commentaires : cite as \cite{cpc85} \\ and should be in bibliography as \\

\textsc{Bohnet} François, art. 85 CPC, in : Bohnet François et al. (édit.), Code de procédure civile commenté, Bâle 2011.

Bohnet François /Haldy Jacques /Jeandin Nicolas /Schweizer Philippe /Tappy Denis (edit.), Code de procédure civile commenté, Bâle 2011

\end{document}

Main.bib

@book{bohnetLivre,
  author        = {Bohnet, François},
  title         = {Procédure civile},
  edition       = 2,
  date          = {2014},
  location      = {Bâle},
  label         = {Procédure}
}

@book{bohnetSchema,
  author      = {Bohnet, François},
  title       = {La procédure civile en schémas},
  date        = {2014},
  location    = {Bâle},
  label         = {Schéma}
}

@book{bohnetActions,
  author        = {Bohnet, François},
  title         = {Actions civiles},
  subtitle      = {Conditions et conclusions},
  date          = {2014},
  location      = {Bâle},
  label         = {Actions}
}

@collectif{coCPC,
  editor        = {Bohnet, François and Haldy, Jacques and Jeandin, Nicolas and Schweizer, Philippe and Tappy, Denis},
  title         = {Code de procédure civile commenté},
  date          = {2011},
  location      = {Bâle},
}

@inbook{cpc85,
  author        = {Bohnet, François},
  title         = {art. 85 CPC},
  date          = {2011},
  location      = {Bâle},
  label         = {Commentaire},
  crossref      = {coCPC},
}

biblatex-xawi.bbx

\ProvidesFile{biblatex-xawi.bbx}[2018/04/13 v1.1 alpha)]

% Depencances
\RequireBiber[2]
\RequireBibliographyStyle{authortitle}

% Localisation
\NewBibliographyString{thesis,habilthesis}

\DefineBibliographyStrings{french}{
  citedas     = {cit\'e},
  thesis      = {th\`ese},
  habilthesis = {th\`ese d'habilitation},
}

% --- --- Setting default options --- --- %    
\ExecuteBibliographyOptions{%
    maxbibnames=99, % nombre max. de noms pour les entrées
    maxcitenames=99, % nombre max. de noms pour les citations
    mincrossrefs=1, % nombre min pour les références croisées
    bibwarn=false, % avertissement uniques pour les entrés bibliographiques
    dashed=false, % Nom entier même si répétition
    singletitle=true, 
    uniquename=full,
    uniquelist=true
}

% --- --- Formatage général de la bibliographie --- --- %

% Formatage des paramètres de la bibliographie
\setlength{\bibhang}{0pt}
\setlength{\bibitemsep}{1.5\baselineskip}

% Formatage global :
\DeclareFieldFormat{title}{\mkbibemph{#1}}

% Dans les citations, pas d'espaces entre les slash (contrairement à la bibliographie)
\renewcommand*{\multinamedelim}{\ifcitation{\slash}{\addnbspace\slash\addspace}}
\renewcommand*{\finalnamedelim}{\multinamedelim}
% BibLatex v2.8+ : Format des séparateurs entre les noms: des slash
% \DeclareDelimFormat{multinamedelim}{\slash}
% \DeclareDelimFormat[bib,biblist]{multinamedelim}{\addnbspace\slash\addspace}
% \DeclareDelimAlias{finalnamedelim}{multinamedelim}%

\renewcommand*{\multilistdelim}{\slash}
%\renewcommand*{\multilistdelim}{\addnbspace\slash\addspace}
\renewcommand*{\finallistdelim}{\multilistdelim}

\renewcommand*{\newunitpunct}{\addcomma\space}
\renewcommand*{\revsdnamepunct}{}

\DeclareNameAlias{sortname}{family-given}

% Remove all possible shorthand
% https://tex.stackexchange.com/questions/244714/how-to-disable-the-use-of-shorthands-in-biblatex
\DeclareFieldInputHandler{shorthand}{\def\NewValue{}}

% --- --- Pilote de bibliographie pour les ouvrages collectifs --- --- %

\DeclareFieldFormat[collectif]{title}{#1}
\DeclareFieldFormat[collectif]{editor}{#1}

\DeclareBibliographyDriver{collectif}{%
  \usebibmacro{bibindex}%
  \usebibmacro{begentry}%
  \usebibmacro{editor}%
  \setunit{\printdelim{nametitledelim}}\newblock
  \usebibmacro{title}%
  \newunit\newblock
  \usebibmacro{location+date}%
  \setunit{\addspace}%
  \usebibmacro{citedas}%
  \setunit{\bibpagerefpunct}\newblock
  \usebibmacro{pageref}%
  \newunit\newblock
  \iftoggle{bbx:related}
    {\usebibmacro{related:init}%
     \usebibmacro{related}}
    {}%
  \usebibmacro{finentry}}

\DeclareBibliographyDriver{book}{%
  \usebibmacro{bibindex}%
  \usebibmacro{begentry}%
  \usebibmacro{author}%
  \setunit{\printdelim{nametitledelim}}\newblock
  \usebibmacro{maintitle+title}%
  \newunit\newblock
  \printfield{edition}%
  \newunit\newblock
  \usebibmacro{location+date}%
  \setunit{\addspace}%
  \usebibmacro{citedas}%
  \setunit{\bibpagerefpunct}\newblock
  \usebibmacro{pageref}%
  \newunit\newblock
  \iftoggle{bbx:related}
    {\usebibmacro{related:init}%
     \usebibmacro{related}}
    {}%
  \usebibmacro{finentry}
}

% --- Formatage de la citation spécifique dans la bibliographie --- %

\newbibmacro{citedas:cite}{%
  \begingroup
    \delimcontext{cite}%
    \DeclareFieldFormat{bibhyperref}{##1}%
    \csuse{blx@hook@cite}%
    \csuse{blx@hook@citekey}%
    \undef\cbx@lasthash
    \undef\cbx@lastyear
    \citetrackerfalse\pagetrackerfalse\backtrackerfalse
    \defcounter{maxnames}{\blx@maxcitenames}%
    \usebibmacro{cite}%
  \endgroup
}

\newbibmacro{citedas}{%
  \ifsingletitle
    {}{
        \printtext[parens] {%
            \bibstring{citedas}%
            \addcolon\space
            \usebibmacro{citedas:cite}
        }
    }
}

\renewbibmacro*{location+date}{%
  \printlist{location}%
  \setunit*{\addspace}%
  \usebibmacro{date}%
  \newunit
}

\newbibmacro{thesis:type+origlocation}{%
    \printfield{type}%
    \setunit*{\addspace}%
    \printlist{origlocation}%
    \newunit
}

\endinput % seulement à la fin

biblatex-xawi.cbx

\ProvidesFile{biblatex-xawi.cbx}[2018/04/13 v1.0 alpha]

\RequireCitationStyle{authortitle}

\DeclareFieldFormat*{citetitle}{#1}
\DeclareDelimFormat{nametitledelim}{\textendash}

% --- Formatage de la citation spécifique dans les citations --- %    
% Definition de la partie "Labeltitle"
\DeclareLabeltitle{%
  \field{label}
  \field{shorttitle}
  \field{title}
  \field{maintitle}
}

\renewbibmacro*{cite}{%
  \iffieldundef{shorthand}
    {\ifnameundef{labelname}
       {\usebibmacro{cite:title}}
       {\ifsingletitle
          {\printtext[bibhyperref]{\printnames{labelname}}}
          {\printnames{labelname}%
       \setunit{\nametitledelim}%
       \usebibmacro{cite:title}}}}%
    {\usebibmacro{cite:shorthand}}}

\renewbibmacro*{textcite}{%
  \ifnameundef{labelname}
    {\ifnumequal{\value{citecount}}{1}
       {\usebibmacro{prenote}}
       {}%
     \iffieldundef{shorthand}
       {\usebibmacro{cite:title}}%
       {\usebibmacro{cite:shorthand}}}
    {\ifthenelse{\ifsingletitle\AND
                 \(\iffieldundef{prenote}\OR\value{citecount}>1\)}
       {\printtext[bibhyperref]{\printnames{labelname}}}
       {\printnames{labelname}%
    \setunit{%
      \global\booltrue{cbx:parens}%
      \addspace\bibopenparen}%
    \ifnumequal{\value{citecount}}{1}
      {\usebibmacro{prenote}}
      {}%
    \iffieldundef{shorthand}
      {\usebibmacro{cite:title}}%
      {\usebibmacro{cite:shorthand}}}}}

\endinput

biblatex-xawi.dbx

\ProvidesFile{biblatex-xawi.dbx}[2018/04/18 v1.1]    
\DeclareDatamodelEntrytypes{collectif}    
\endinput