That would probably be possible, though it might be pretty hard to get anyone to actually start working on it ...
Anyway, FF8 uses a DLS file to begin with (kind of like a "software-based" soundfont solution), so changing instrument sounds is not very hard (even with the voices, etc. in some songs). In FF7, you could only do this if you had a sound card that supports soundfonts, or by changing the music to something other than MIDI via FF7Music. You should check out Samuel Slight's FF8 DLS
here, if you haven't yet -- It may not sound exactly like the PlayStation version, but it sounds pretty nice.