Yes! I was very surprised they Keystep doesn't do this already, with all those step buttons when you go into arp mode! This behavior is ubiquitous enough that it is the norm for arpeggiators, though most (mini nova, Microkorg) are 8 step patterns, having the full 64 would be truly awesome, even just 16 would be great...
if memory is an issue the existing pattern for the sequencer could double (if enabled) as the rhythmic setting for the arpeggiator...
- Joel