Yes it is.
Most Multi FX processor units can do that without a problem. Just look for processors with stereo in and outs. Like the good old Boss SE50 and SE70 for example.

Even cheaper stuf by Line 6 (like their modulation FX box) has stereo ins and outs and can phaze the signal by either modulating the stereo signal or modulating L/R sides separately and phazing them in the opposite directions.

Cancelation isn't going to be an issue

-ED-