So really what you are saying is because he is an openly gay guy he cannot or should not be cast in a heterosexual role. Rupert Everett was clearly right then when he said that performers should not necessarily come out. I thought this was the 21st century? So you have to be a murderer to play Macbeth? It is clearly a good job the "crowds....of women" are not aware that many of their favourite TV actors and presenters are gay but choose to keep their private lives private for the sake or their careers.
Should Will Young be cast - he will no doubt be very charismatic in the role with a spendid voice and excellent chemistry with his leading lady - it's called acting.