dietsche (./7) :
2) drop support for old AMS versions; it is easy to upgrade with a link cable or PC. This reduces complexity of the project. It might be pretty safe to pick the very latest versions of the OS. I don't think TI puts much effort into these calculator models anymore, so future OS versions are somewhat unlikely.

Why do you exactly have in mind by dropping the support of old AMS versions?
The tigcclib hacks for getting some romcalls on old AMS? Or increasing the MIN_AMS bu default?