As the process has evolved, I've explored the idea of a fixed improvisation setup - i.e. in the Streamland instrument, having several sample slots and effects pre-loaded and pre-MIDI-mapped. This way, at least a core set of controls could get into my muscle-memory, and I could develop a more immediate and focused auditory-tactile relationship, relying less on my eyes.
What eventually evolved was not to have anything pre-mapped, but rather to just develop a flexible consistency. This generally involved:
-sample on-off triggers and sample reverse buttons in the same place on the QWERTY keyboard each time
-volume faders mapped to the same or similar places (depending on what samples need a fader, and what could be grouped together on a single fader)
-core effects mappings - for the basic effects setup that has been used almost everytime, and sometimes augmented with additional effects - dials mapped to delay time, delay feedback, reverb room size
This would typically result in the entire control setup consisting of approximately:
-20 QWERTY keys
-and the laptop track-pad
This setup is also completely portable - MIDI mappings were done with an Icon iControl, and I've now switched to a Korg NanoKontrol. Apart from this, just a laptop and headphones.