I would love this.
Regarding the problems with internal modulation to fx - would it be possible to do it as the hapax does, where the effects 'lanes' include a mod/attenuation matrix, and there are also lfo/envelope effects that can be placed within the effect 'lanes' with access to their adjacent effects?
I suppose then the question would be, how much is the 3 effect slot limit a matter of available processing/memory resources - or was it just set conservatively? The hapax had 8 slots per track, plus the mod matrix, and it was easy to use a fair chunk of it if you had say lfo, harmonizer, arp, scale quantising, velocity modulation, tranposition.