Impressive...about the only thing I would want to substitute out would be to toss one of those triple VCA/mixers in favor of some sort of delay line in that 6hp space. Ambient really sort of needs some sort of sound-field depth manipulation in order to get that immersive quality, and delays seem to be better in restrictive spaces than the reverbs that one might fit in the same space. Plus, with the sequencer, you'd then have the ability to do very Berlin-school-ish 'delay canon' repetitions if the delay can sync to the sequencer clock. While it's spendy, still have a look at Audio Damage's ADM16 Dub Jr....does all of this, plus gives you the fun of an insert in its feedback path. But another way to do this and have even more flexibility would be to go with an effect send/return module such as Malekko's SND/RTN, which would allow you to insert a number of chained outboard devices AND give you another 2 hp to drop a VCF in from...who else?...2hp. You kinda might want a VCF in this, come to think of it.