I had a unit years ago (which I dont want to name as theyre hard enough/impossible to find already) which had a tempo-adjustable (via internal bpm settings or external midi) 4 tap delay with adjustable feedback and a hold function.
But one the unit was in ‘hold’ mode, the taps could be slid forward or back in beat subdivisions and very interesting rhythms could be made.
Something similar in function for the H9 would be incredibly useful