As audio tracks are just long time-stamped samples/audio phrases played from RAM and triggered by the transport, it doesn't strike me that resources would be that much strained if there were to be more. As the MV can handle 512 audio phrases and 9,999 samples plus 128 patches in a project (depending on size of RAM) it seems there is power to spare that often goes unused.
The mixer is a different thing. Might have to have an option to mix fewer MIDI parts to make space?
Polyphony of 64 notes is a limitation. 32 notes are priority assigned to the 8 audio tracks. So each track uses 4 notes? Presumably to allow for one level of undo.
Personally I find the note capacity of approx. 150,000 notes too small. It would be nice to see that increased. Even the ability to use a PS2 keyboard might come in handy.