Updating the document class to have a font size of 14 pt

Question

I have the following document class (.cls) for my thesis book:

%
% ociamthesis v2.2
% By Keith A. Gillow <gillow@maths.ox.ac.uk>
% Version 1.0 released 26/11/1997
%-------------------------- identification ---------------------
\NeedsTeXFormat{LaTeX2e}
\ProvidesClass{ociamthesis}[2010/11/22 v2.2 OCIAM thesis class]
%-------------------------- initial code -----------------------
\def\logoversion{squarelogo}
\DeclareOption{beltcrest}{\def\logoversion{beltcrest}}
\DeclareOption{shieldcrest}{\def\logoversion{shieldcrest}}
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{report}}
\ProcessOptions\relax
\LoadClass[a4paper]{report}
% As an alternative to the above could use next line for twosided output
%\LoadClass[a4paper,twoside,openright]{report}
\RequirePackage{graphicx} % needed for latest frontpage logo
\RequirePackage{ifthen}   % needed for option parsing for logo
\raggedbottom
%define the default submitted text
\newcommand{\submittedtext}{{This book is based on the doctoral thesis.}}
%
% DECLARATIONS
%
% These macros are used to declare arguments needed for the
% construction of the title page and other preamble.
% The year and term the thesis is submitted 
\def\degreedate#1{\gdef@degreedate{#1}}
% The full (unabbreviated) name of the degree
\def\degree#1{\gdef@degree{#1}}
% The name of your Oxford college (e.g. Christ Church, Pembroke)
\def\college#1{\gdef@college{#1}}
%
% Setup choosen crest/logo
%
\ifthenelse{\equal{\logoversion}{shieldcrest}}%
{
% Traditional Oxford shield crest
%Using latex metafont (Mathematical Institute system)
\font\crestfont=oxcrest40 scaled\magstep3
\def\logo{{\crestfont \char1}}
%For comlab system replace 1st line above with
%\font\crestfont=crest scaled\magstep3
}{}
\ifthenelse{\equal{\logoversion}{beltcrest}}%
{
% Newer Oxford Belt crest
%Using latex metafont (Mathematical Institute system)
\font\beltcrestfont=oxbeltcrest
\def\logo{{\beltcrestfont \char0}}
%For comlab system replace 1st line above with
%\font\beltcrestfont=newcrest
}{}
%\ifthenelse{\equal{\logoversion}{squarelogo}}%
%{
%% Latest Logo, Square version (the default!)
%% you need an oxlogo.eps or oxlogo.pdf file as appropriate
%%\def\logo{{\includegraphics[width=41mm]{essexlogo.jpg}}}
%\def\logo{{\includegraphics[width=34mm]{UoE_COA.jpg}}}
%}{}
%
% Define text area of page and margin offsets
%
\setlength{\topmargin}{0.0in}
\setlength{\oddsidemargin}{0.5in}
\setlength{\evensidemargin}{0.5in}
\setlength{\textheight}{9.0in}
\setlength{\textwidth}{6.0in}
%
% Environments
%
% This macro define an environment for front matter that is always 
% single column even in a double-column document.
\newenvironment{alwayssingle}{%
       @restonecolfalse
       \if@twocolumn@restonecoltrue\onecolumn
       \else\if@openright\cleardoublepage\else\clearpage\fi
       \fi}%
       {\if@restonecol\twocolumn
       \else\newpage\thispagestyle{empty}\fi}
%define title page layout
\renewcommand{\maketitle}{%
\begin{alwayssingle}
    \renewcommand{\footnotesize}{\small}
    \renewcommand{\footnoterule}{\relax}
    \thispagestyle{empty}
  \null\vfill
  \begin{center}
    { \Huge {\bfseries {@title}} \par}
{\large \vspace{40mm} {\logo \par} \vspace{25mm}}
    {{\Large @author} \par}
%{\large \vspace{1ex}
%    {{@college} \par}
%\vspace{1ex}
%    {University of Essex \par}
%\vspace{25mm}
%    {{\submittedtext} \par}
%\vspace{1ex}
%    {\it {@degree} \par}
%\vspace*{2ex}
%    {@degreedate}}
  \end{center}
  \null\vfill
\end{alwayssingle}}
% DEDICATION
%
% The dedication environment makes sure the dedication gets its
% own page and is set out in verse format.
\newenvironment{dedication}
{\begin{alwayssingle}
  \thispagestyle{empty}
  \begin{center}
  \vspace*{1.5cm}
  {\LARGE }
  \end{center}
  \vspace{0.5cm}
  \begin{verse}\begin{center}}
{\end{center}\end{verse}\end{alwayssingle}}
% ACKNOWLEDGEMENTS
%
% The acknowledgements environment puts a large, bold, centered 
% "Acknowledgements" label at the top of the page. The acknowledgements
% themselves appear in a quote environment, i.e. tabbed in at both sides, and
% on its own page.
\newenvironment{acknowledgements}
{\begin{alwayssingle} \thispagestyle{empty}
\begin{center}
\vspace*{1.5cm}
{\Large \bfseries Acknowledgements}
\end{center}
\vspace{0.5cm}
\begin{quote}}
{\end{quote}\end{alwayssingle}}
% The acknowledgementslong environment puts a large, bold, centered 
% "Acknowledgements" label at the top of the page. The acknowledgement itself 
% does not appears in a quote environment so you can get more in.
\newenvironment{acknowledgementslong}
{\begin{alwayssingle} \thispagestyle{empty}
\begin{center}
\vspace*{1.5cm}
{\Large \bfseries Acknowledgements}
\end{center}
\vspace{0.5cm}}
{\end{alwayssingle}}
% STATEMENT OF ORIGINALITY (AS SUGGESTED BY GSW)
%
% The originality environment puts a large, bold, centered 
% "Statement of originality" label at the top of the page. The statement 
% of originality itself appears in a quote environment, i.e. tabbed in at 
% both sides, and on its own page.
\newenvironment{originality}
{\begin{alwayssingle} \thispagestyle{empty}
\begin{center}
\vspace*{1.5cm}
{\Large \bfseries Statement of Originality}
\end{center}
\vspace{0.5cm}
\begin{quote}}
{\end{quote}\end{alwayssingle}}
% The originalitylong environment puts a large, bold, centered 
% "Statement of originality" label at the top of the page. The statement 
% of originality itself does not appears in a quote environment so you can 
% get more in.
\newenvironment{originalitylong}
{\begin{alwayssingle} \thispagestyle{empty}
\begin{center}
\vspace*{1.5cm}
{\Large \bfseries Statement of Originality}
\end{center}
\vspace{0.5cm}}
{\end{alwayssingle}}
%ABSTRACT
%
%The abstract environment puts a large, bold, centered "Abstract" label at
%the top of the page. The abstract itself appears in a quote environment,
%i.e. tabbed in at both sides, and on its own page.
\renewenvironment{abstract} {\begin{alwayssingle} \thispagestyle{empty}
  \begin{center}
  \vspace*{1.5cm}
  {\Large \bfseries  Abstract}
  \end{center}
  \vspace{0.5cm}
   \begin{quote}}
{\end{quote}\end{alwayssingle}}
%The abstractlong environment puts a large, bold, centered "Abstract" label at
%the top of the page. The abstract itself does not appears in a quote
%environment so you can get more in.
\newenvironment{abstractlong} {\begin{alwayssingle} \thispagestyle{empty}
  \begin{center}
  \vspace*{1.5cm}
  {\Large \bfseries  Abstract}
  \end{center}
  \vspace{0.5cm}}
{\end{alwayssingle}}
%The abstractseparate environment is for running of a page with the abstract
%on including title and author etc as required to be handed in separately
\newenvironment{abstractseparate} {\begin{alwayssingle} \thispagestyle{empty}
  \vspace{-1in}
 \begin{center}
    { \Large {\bfseries {@title}} \par}
    {{\large \vspace{1ex} @author} \par}
{\large \vspace{1ex}
    {{@college} \par}
    {University of Oxford \par}
\vspace{1ex}
    {{\it \submittedtext} \par}
    {\it {@degree} \par}
\vspace*{2ex}
    {@degreedate}}
  \end{center}}
{\end{alwayssingle}}
%ROMANPAGES
%
% The romanpages environment set the page numbering to lowercase roman one
% for the contents and figures lists. It also resets
% page-numbering for the remainder of the dissertation (arabic, starting at 1).
\newenvironment{romanpages}
{\cleardoublepage\setcounter{page}{1}\renewcommand{\thepage}{\roman{page}}}
{\cleardoublepage\renewcommand{\thepage}{\arabic{page}}\setcounter{page}{1}}

In my .tex file I use the following line of code to have the font size as 12 pt:

\documentclass[12pt]{ociamthesis}

My book's final dimension will be 6 inches x 9 inches. I am trying to update the font size of the thesis book content to 14 pt but even after updating the LaTex class I am not able to achieve that.

I have tried to update the .cls file to have the following code for the purpose:

\LoadClass[a4paper]{report}
\newcommand{\@xivpt}{14}
\DeclareOption{14pt}{
  \renewcommand{\normalsize}{\fontsize{\@xivpt}{18}\selectfont}
  \renewcommand{\small}{\fontsize{\@xiipt}{14}\selectfont}
  \renewcommand{\footnotesize}{\fontsize{\@xpt}{12}\selectfont}
}
...
...
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{report}}
\ExecuteOptions{14pt,oneside,openright,final}

However, my update of the .cls file is not updating the document's font size to 14 pt. How can I successfully update the .cls file to have the specified font size?