What are the chances this would run on CM4 instead?

It should run ok on a CM4, but with some limitations.

Less DSP headroom; swatcoder's optimization suggestions in this thread become more important. Simultaneous 4-part polyphony might push things. You'd probably want at least a 4GB board.

Also, the brumectl installer will not attempt to set up the USB audio/MIDI bridge (Meridian) on a CM4. That auto-configures only on a CM5 for now.

Would be a pretty light lift to get that working if you are interested.