Would require lots of porting i guess since 64 bit types != 32 bit types (example 64 bit uses long long integers while 32 bit uses long integers) could probably get it to compile pretty quickly,
but i know from experience that things can and will fuck up

besides win 7 64 can run 32 bit executables just fine but yeah you need 32 bit dll's then.
A workaround would be to link quakespasm to the static libraries for those dll's that way you can have side by side executables.
Productivity is a state of mind.