I used to use a MOTU MidiExpressXT in my previous setup (the old model), and it worked wonders.
Unfortunately is serial parallel port only, and I’m now using my AMT (which was in the closet for a long time.
AMT can only reroute from port to port (not rechannelize), so it cannot work as a proper standalone patch-bay, and at least on PC they have at times some timing problems over USB (that’s why it was closed in a closet).
Anyway I managed to set up a fairly complex routing in Cakewalk (and a slightly simpler one with Live) in an hour or so, I now have a nice map with which instrument channels responds to what Octopus channel. So I don’t think it would be a problem with Logic.
With this set-up I do save the midi together with the audio, as a precaution and because usually I don’t really need to save the pages in the Octopus.
Anyway, I’d like to work less with the computer, so I’ve got a saved search on ebay for motu midi express xt (usb) [ain’t got spare pci ports].