No, a waste of time idea...
We are chrono'd now for safety reasons and because people cannot be trusted to set their own markers up to shoot below the required fps for any given tournement.. having a "built-in" chrono is not going to change that.
As for using them to control the reg you can, in my opinion, link it to the bolt/breech/barrel/trigger as much as you need to (personally I think if they do it they will link it to the dwell) but it should not be allowed on field as there is the potential for it to start firing hot during the game BY DESIGN if you are going to try and make the fps limit anywhere up near 300fps.
If you're not going to try and get it that high then what's the point in having it self-regulate? Most electro's these days seem to be within +/- 10fps so set the marker to 290fps, lock the reg, and leave it alone.
I can honestly see no reason for a chrono on a marker.
Urban