The Problem..........
............. with Mandy is that he might have to resign, if past form is anything to go by.
There are some countries where they appoint/elect their head of state but more often than not they're a pretty dull cove. The exception that springs to mind is Mary McAlesse: the Irish President. From what I understand, she is very well regarded and is a role model for other heads of state who are not heriditary.
If we were to forced into abolishing the monarchy, I cannot think of anybody I should wish to have as head of state, who has the gravitas, respect of the public or intelligence to carry off the role. That said, when one of the old Commonwealth countries decides to leave the 'club', it will be fascinating to see how they go about it and who the make head of state.
O-D