I think what your asking for is not a delay effect at all, but a dynamics effect. I've never heard of a delay pedal doing volume swell. It's like asking a shovel to do the job of a hammer.
Volume swells in processors are usually achieved by a slow noise gate. Once I had a multi-effects processor that did this, but it was because the processor had both delay and dynamics effect like a gate built in. I'd suggest setting a good compressor or gate with a slow attack time in front of your delay.
On the other hand, the MODfactor DOES have some volume control effects. The Tremolo effect basically just raises and lowers volume. I could see this effect being tweaked or updated by Eventide to allow volume swells, but not the TimeFactor.
