if the UK's head of state is to be determined by any means other than the current system, then we would do well to heed the words of douglas adams:-
"One of the many major problems with governing people is that of whom you get to do it; or rather of who manages to get people to let them do it to them: It is a well known fact, that those people who most want to rule people are, ipso facto, those least suited to do it. Anyone who is capable of getting themselves into a position of power should on no account be allowed to do the job."