The main issue is the sheer CPU cost of doing so.. especially those reverb units. E2 doesn't do core-spanning. Yet. It would need to if we want to go there.There is no law saying that effects cannot exist upstream of MPE channel summing. Obviously my wish can’t come true without a newly designed type of pre-summing fx slot, that’s why I called it a dream, indicating that I don’t really expect it to happen any time soon. But of course it is totally possible to pull off.
But what is polyphonic is the effects routing. This is a feature (also present on Cypher2) whose power is much underrated. Not only for the obvious MPE reasons (reverb send on SLIDE? yes please..), or well-worn layering tricks - but, for example, you can use one of the envelopes to send just the first or the last part of the sound (time domain wise) to a delay or reverb FX. So you can get delay reflections that just capture the attack transient - or exclude it for a seamless, hazy reverb wash.