I have a cheap and cheerful solution to this based on the random evolution of my system.
I had an old NI audio interface - Komplete Audio 6 I think with four channels. I then got hold of a couple of the Roland Eurorack fx units (scooper and demora) as they were being sold off cheap.That equals eight channels of in/out. Set them up as an aggregate device on the Mac, it works perfectly.
My workflow is to multitrack live patching from the modular and then tidy up and mix a little after in the box, but as little as possible.
However, I do toy with the idea of getting a rackable single unit with 8+ inputs - there seems to be a decent amount of choice out there.