It's possible but it would break the paradigm a bit; HomeWave in principle always follow along with whatever happens on Vera, it is not meant to implement control logic.
I have similar momentary switches based on the Fibaro relay; they toggle on and then off again, but report the "off" state to Vera as well, which passes it on to HomeWave. If Mimo doesn't report its state instantly back to Vera, then you could fix this with a Scene that is triggered by the Mimo turning on, and turns it off.
You could also use an "action" button to send the lu_action string to Vera to turn the Mimo on. The action button doesn't track the unit's state, so the next time it is pushed it'll simply send the On command to Mimo again.
If there are more use cases for implementing a momentary push button, let me know! If there is enough demand, I can implement it.