The ability to have multiple (indexed) subloops as elements of the 'loop' (loop concept used here as decoupled from a fixed-time paradigm, but used more as a logical entity). The subloops would have an arbitrary repetition time.
This eliminates the restriction of one repetition period per loop (as dictated by the Repeater). Other looping devices currently may have this differently, don't know about the EDP e.g.
Furthermore, if combined with the possibility to assign measure (bar/beat numbering) and a beat quantize capability, this would enable the buildup, superimposition and individual manipulation of loops that are a defined ratio of time to one another - I.e., true polyrhythm. E.g., my first loop element is a 12/8 but my next loop element (within that loop location) is a 5/8. (BTW herein lies also the added value over having separate loopers doing the multiple-loop thing, other than cost).
The polyrhythm in the Repeater is a gross misnomer. It is merely the assignability of arbitrary (odd, prime, whatever) meter to what's already in the fixed-length loop.
I have more, equally ill-thought-out ideas... How about (MIDI) pitch shift *during* record?