I would hope in fact that the monarchy may in fact gain more of it's traditional powers if the two young princes do join the military... at least allow the prime minister & parilment to cede a little bit of his military capabilities back to them if they seek military command similar to that of generalship... it would be intresting to see a king in the field direcing operations again, especially if the forieng policy is kept in the hands of the PM!
(in other words, a super-general with real power, but only if they earn the right)