To the best of my knowledge, this isn't possible from within a single preset.

Just an idea, but couldn't you use a boost, overdrive, or distortion pedal for this? I'm not aware of any delay pedals from any manufacturer that have a feature like this. I believe that the preset volume that has been added to V3 is meant as a way to balance the effect vs. bypass level, not as a volume boost.

If you really want the TF to do this, couldn't you use 2 presets with differing output levels but all other parameters the same? I know that would use half of the presets for basically duplicate settings, but how many completely different presets do you really use during a gig (not counting tempo changes)?