That is a good way to simplify - running splits in the exs24.
I don't really use exs24 very much live, aside from piano. I usually use an ES2 patch or 3rd party such as Garritan Personal Orchestra or the GForce Mellotron plugin.
The biggest risk for me is the whole computer crashing, or midi keyboards stop working, requiring a reboot - which is as least 5 minutes of setup. Unfortunately I have my guitar plugged into the computer for SL now, so doing a little acoustic number is out of the question. I'd also need to be setting stuff up - the midi learning in MS, firing up midi routing, making sure SL works, etc.
It's probably best to have an mp3 player plugged into the sound system! I know that some pros have two laptops set up. But really, most of the shows we play have about 10 people actually watching, so I don't think it would be a big deal to have a 5 minute break.
I'll probably do a little video on setting up the routing in logic - getting the switches to work wasn't the most intuitive thing.
And you're very welcome