if your only use case is to disengage the regen braking you should probably just have a regen braking disable function, a clutch is an awfully complicated way to achieve that. You could literally have a software 'clutch' pedal that did nothing other than disable the regen if that was your goal.
Although on the other hand the clutch does have a nice property, which is that it works regardless of the state of the control system of the vehicle. If my MCU decides it wants to accelerate me at 500 mph into a wall a hardware clutch would be a nice thing to have!
W.r.t gearboxes in EVs: there is definitely a reason to have a transmission in an EV, it's just that most manufacturers don't include one for simplicity .