Two Person Live Stem Mixing: Need gear advice

We are an Electronic/Production duo looking to go from an expanded live setup (using guitars, live drums, keys, etc...) to more of a compact "Live Stem Mix" type of show.

We're looking at moving from Logic Pro (which ran a modified backing track) to Ableton. As I understand, Logic Pro isn't really fit for what we're trying to do, whereas Ableton is.

The idea is this:

Two of us behind the table on 1 laptop running Ableton. Set would be predetermined due to the fact that we're stem mixing, but it would be nice to cue up a set of 4 stems at once in order to improvise and add a mix in if appropriate (don't believe that's possible). At this point we'd be playing most of our own stuff (between 2-3 album's worth of material).

One has a "Main controller" possibly Novation Twitch, NI S2, or Novation's Zero SL MKII. This controller would provide mixing, cueing and minimal track modification (effects, gates, etc...)

The other would be manning an APC40 controlling 4 separate tracks and modifying each one using effects, gates, filters, etc...

Finally we'd have an iPad setup with the Lemur iOS app for triggering samples and vocal chops.

The question is this:

Would Ableton natively support Twitch + APC40, or another combination of that sort? And is there any advantage of doing something like that, as opposed to just using two APC40's?

The Twitch and other DJ Mixing controllers have dials that may come in useful, but as far as how? I haven't figured that out yet. I know that the Twitch has it's own sound card, but I don't believe we'd be using it as the final output will be going through an Apogee Duet. There would be no headphone monitoring required, since the set would be pre determined.

If you've read this far, I'd be interested in hearing your opinion on this type of setup as well as any interesting alternatives you can believe of. The most important aspect is that we want to come off as more of an electronic band while maintaining an interactive and spontaneous live experience.

Edit for clarification: I have noticed that people have trouble with connecting two APC 40's using one Ableton instance. There is mirroring of commands sent from one device to the other. Is there an easy way around it, and would it act the same way with two different controllers like the Twitch + APC?