the trouble is, jake, it is hard to say what constitutional affairs are improperly decided at present. The monarch's right to appoint a prime minister the public don't want seems to be purely theoretical. The only abuse of the power I can remember was the removal of Gough Whitlam in Australia, and even the Australians went along with it, though I wouldn't have. Different countries require different things of their heads of state, from the strong executive in the USA and France to the largely decorative one in the UK. If she's without real power apart from the ability to get the odd BBC controller sacked, then it doesn't seem to me to matter how the role is filled, and an economic argument is as good as any other; a hereditary monarch is no better or worse at opening supermarkets than Jade Goody, but is ore likely to attract American tourists.
There's certainly a case to be made for having an elected head of state, but it requires me to say with a straight face that the Americans under Bush are better off than we are under the queen.