There is an FV1 reverb patch that can do infinite sustain if you max out the reverb control. I have an expression pedal input on my FV1 build that controls that pot so you can ramp it up for the freeze effect.
It’s one of the example ones available on Spins page, I think it’s called reverb-hp-lp or something like that.
If you wanted to get closer to there actual freeze, perhaps you could have the pedal always on and passing signal and then use a foot switch to max (or close to it) the reverb value rather than using it to bypass the pedal.