Maybe a bit self-promotion, but if this approach is what you’re considering you may be interested in Cells! 2.0. Download beta 2 from that thread to experiment and remember to download the manual as it explains everything.
Cells! lets you load in note riffs and samples (grouped by instruments) and mix, modify and generally play around with them in a similar way to session view in Ableton.
Instruments of samples can be loaded / unloaded on the fly while it’s running, so if you prepare all your tracks beforehand you should be able to use this feature as required.
Anyway, just thought I’d point you in to another alternative should you be interested.