There's nothing you can do about the polyphony of the MM8. But you can get around the problem by:
1. Using sound modules via midi, esp when you are layering. This would greatly increase your overall polyphony.
2. Changing the way you play. Be conscious of the limited polyphony, use less sustain (and pedal up frequently), and choose your patches carefully. Note that some patches may have 2 sound elements in them (ie playing one key = 2 notes). That means you polyphony effectively decreases to 16 with some patches.
3. Decreasing the release time of the patches with some programming.
It's not impossible. Just need some conscious effort to change your playing style.