We're using the index package in order to get several indexes (name index, subject index, language index), and we're basically happy with it. There's only one obstinate problem: index does not propagate footnote numbers as desired, unlike makeidx (which doesn't support multiple indexes though):
\documentclass{scrbook}
\usepackage{index}
\usepackage{hyperref}
\def\fn#1#2{%
\hyperpage{#2}n#1%
}%
\newcommand{\is}[1]{\if@noftnote%
\index{#1}%
\else%
\index{#1|fn{\thefootnote}}%
\fi%
}
\makeindex
\begin{document}
\footnote{First footnote.}
\footnote{Second footnote.\is{inside second footnote}}
\footnote{Third footnote.}
\printindex
\end{document}
This outputs inside second footnote, 1n3 instead of inside second footnote, 1n2. Hence, \thefootnote seems to be expanded at the very end, and not immediately in the footnote.
Any suggestions how to do it right with index?

imakeidxis on my agenda. But for now, I wantindexto do the job. – Timm Dec 11 '15 at 15:18