@melkhorn
You are in the OS X forum, so FFADO doens’t matter there;)
@ryan
Yes Ardour can do many more than 16 tracks provided your equipment is up for it. From the sounds of it your interface is, so as long as your computer you are using is up to the task then you shouldn’t have a problem. If you do feel free to ask, there is likely something that can be adjusted to allow you to do it without a problem(For instance longer buffer settings/times on Jack).
Seablade
For the record I have tracked much larger shows without a problem onto my laptop with a SSD, so it all depends on your computer equipment.
The simple answer is yes, Ardour can certainly do that.
The real question is if your friend’s Alesis Multimix 16 is up to the task, audio-wise and with respect to FFADO compatibility.
I’m not familiar with the unit, but a quick scan of the information on the Alesis site says it can send 18 direct outs on firewire, so that seems to be adequate. It does only have 8 mic pres though, so you’d have to come up with a few more (to drive line inputs on the Multimix) to reach your target of 11.
As far as FFADO goes, it’s listed on the FFADO site as “reported to work” probably meaning the developers haven’t had an actual unit to test/verify, but that other people have had success with it.
So, it looks like the basics are in order. You should give it a shot and report back to us:)