Actually, the addition of the EP-420 makes a lot of sense. The form factors of both cases are pretty much a dead match, which means you can implement the 270 as a sidecar...sort of like the ARP 2500 "wing" concept. An interesting idea might be to designate the current 270 as your "control" cab with sequencing and timing, plus MIDI, have the main synthesis in the 420, then add a second 270 for processing and mixing. Plunk the KSP right down in front of the 420, and there you are.
Naturally, this would be "long term" stuff...but it's not a bad idea to explore those ideas NOW so that you'd have a clear idea of how an expanded variation would work.