The thing is the M register is becoming less attractive for private operators at the present time, I'm not sure if there has been a change in management but the risk for someone in your position is that the operator flips over to the G reg and all of a sudden you find yourself not being able to fly the aircraft.
There is a new head of the registry in IoM, but not any change of attitude or professionalism. Have you heard of anybody flipping in the way you suggest (tail #'s please). What I have seen is an every increasing number of M registrations and a bunch of happy clients.
This is the most developed, most accepted and most efficient registry currently..and with a host of advantages over an EU registration as long as you are not seeking to charter the aircraft.