Yeah, Spacetime would be my call too.

One of the extra controls would be output level and the other would make the modulation a little more flexible somehow (maybe make it cover flange to chorus to doubling or some such).

Finally, make it capable of stereo in and stereo out that can be used to drive headphones if desired.

That one pedal would be so useful for guys in the real amp world as well as the modeler-amp-pedal world (especially the Tonex pedal because that could serve as a basic midi controller too).