Great collection!
Are there any very affordable DIY midi control surfaces with a few knobs, pads, keys (two octaves), and BT?
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For programable controllers, the Launchpad series from Novation is pretty handy. I've seen it configured as a sequencer controller among other things.
Just Hackaday have 45 articles on the subject of "MIDI Controller" :) https://hackaday.com/tag/midi-controller/