ModularGrid Rack

This is probably what I would do under those conditions to achieve what you're describing. You can fill up the Disting with samples and stuff before you go so there's plenty of extra drum options. Crust is also good because of the alternate firmwares. Both of those voices can cover a wide range and be more than just a single drum each with clever modulation. Veils is flexible and can be used for multiple things at once (like mixing two tracks of audio on one half and controlling modulation on the other half). Even if you take the Beatstep Pro, I think the Pam's, Tetrapad and Tete are unavoidable here. They seem to be most of your modulation and playability. If anything, the DFAM might be a better accompaniment for this than the Beatstep Pro, but it's all up to you.