(a) such a change would not change the number of strings or characters that can be registered at all: only the base characters can actually appear in an IDNA string post the ToUnicode(ToASCII(char)) operation pair
Interesting idea, but you may lose every chance to have a RHD/LHD common support if you make it too simply. On the countrary it permits to have the information to differentiate upper and lower cases if/when needed.
jfc
