anyway, about the "no capacitive screen + multitouch in N900 = no maemo 6": just make a version with also/instead resistive screen drivers (or whatever software is needed), and disable multitouch gestures? o.o (I imagine it's just question of replacing or disabling one or more software packages..)
for the rest, I don't really see other possible hardware changes... (maybe a digital compass? but I don't see how that would limit OS components..)