How's this?
I dropped the second 1U mixer in deference to adding a stereo FX device from endorphin.es. Once this was changed, this left new room in the tiles for a Mutable Ripples clone (with quad CV in expander), a Duatt for either extra mixing or attenuverters, a MIDI interface in case you want to run this via an external clock or another sequencer, and the proper Intellijel Stereo Out so that the Palette's 1/4" jacks can be used here. Yes, I know it's mainly a sequencing rig...but one last curveball here just for that: a Ladik dual gate/trig delay so that you can slip a little "slop" into a couple of the drum trigger paths...controllable manually or via the Apex. This'll make things humanize a little, or you can "slip" one or two drums for a hint of syncopation.
With the Shuttle System, this thing'll seriously walk that walk!