All it has got is the bare minimum OEMDrivers, plus a fully featured SYS (some of the SYS applications have been tweaked: removed extra screen layouts for LockScreen, removed SampleMusic etc, UPXed a few things).
The XIP has been tweaked quite heavily to get the best performance, and you should be able to add whatever you like to this ROM and it should remain stable.
Try it and see (and install whatever keyboard you feel like using).
This will probably act as the basis for some "full" ROMs afterwards.
A few screenshots of this ROM (on a Diamond)
New build (09090401)