I know what you mean, basically, wanting to step through the presets in sequential fashion either up or down. Unfortunately, that's not possible with any of the Factors, with or without AuxSwitches. The previous Factors had 2 presets available in one bank, but even with an AuxSwitch, you still had to select one of them after changing banks in either direction.
I think the dilemma is that, if the next or previous preset was instantly activated, there wouldn't be any way to get to non-sequential presets without going through every preset between. Given that each preset takes a small amount of time to load, moving through 20 presets could take somewhat longer and would definitely be clunky for live use. If there were only 2 or 3 presets, it wouldn't be a big deal, but each of the Factors has 100 presets (you can limit the number available, though).
The alternative method, selecting which preset you want and then activating it, may take 2 (or more) taps of a footswitch, but that's the method that's been in use by almost all MIDI addressable devices since MIDI was introduced. Arguably, this is much more flexible; you wouldn't be tied to a sequential order of presets.
A possible solution would be to incorporate a MIDI Controller, one that could allow you to instantly access several presets (depending on the size and capabilities of the controller).
Another alternative is to suggest that Eventide adds something like a "preset activation mode" option to the Utility settings. Not necessarily a bad idea, but it might be confusing for some users.
