5) Explorer Integration - Will Explorer.exe need to be
rewritten to
allow the addition of Metadata structures, etc.
Not rewritten - maybe extended to be able to query the additional
information.
call me silly, but can't this be done via a shell extension without
having to touch explorer?
Depends on what you are trying to do exactly.
And "extending explorer" includes things like touching shell32.dll
for me. You can't look at them separately for most features,
they are just too much integrated.