Four knobs is probably all you'll need! They're all multi-function. Turn for one thing, hold down and turn for another, tap for another, etc.
A bit of tech info. I'm using an atmega644 uC. It's got 64KB program memory but so far I'm using only 17% of it. I needed the 2KB of eeprom it offered for preset storage. When recording custom LFO shapes, it samples at 10 a second for up to 18 seconds. And then it's interpolated times 20 to smooth it out. Speed is full adjustable while recording and after, obviously. 10sps is plenty for slow human hands, but I'll offer the user to fine tune this in a sort of "preferences" mode.
Let's see, checklist. What's done, and to-do..
-hook up PWM output (with freq doubling)
-do custom LFO record/playback
-square/triangle/ramp/sine/saw hard preset LFOs
-multimode tap footswitch
-clean tl074 buffer