Creating Looping specific tracks for live performance

[Young Echo]

I'm building a set for playing live shows, mixing synths and clips on Ableton Live and live musicians. All good so far.

I've looked and looked to try and find a solution to creating Live loops on the fly whenever we want during the set, and maybe it's straightforward and I'm just an idiot:

We've got clips and scenes set up for various songs, with quite a bit of leeway so that we can extend parts if we want to create tension particularly on intros and breakdowns. What I want to do though, is allow our percussionist to create loops "on the fly" using drum pads, clicking in and out, overdubbing the loops whenever he wants - and of course, stopping the loops and clearing the clip ready for the next time he feels like improvising drum loops.

These loops should be independent of scenes being launched, so that we can really build the tracks through different chord progressions etc, but keep the drum loop that's been looped going - and building on it if necessary. Problem is, I can't work out how best to make this work. It's easy enough to set up the midi mapping through an FCB1010 or whatever, but I can't see how we can get it going. Creating a dummy clip of 4/8 bars is an option, but how to trigger this recording/overdub/stop independent of the main track control?

Further to this, we'd also like to do a similar thing with vocals - which I guess will use Looper, but again we don't want to to be reliant on the scene launch/changing. We want to take advantage of the loops being in time etc, but sort of act as independent devices.

Any ideas? Feel free to abuse me for being an idiot and not seeing what's right in front of my eyes!

Thanks