>if Queen thought 'We Will Rock You' sucked as an idea,
What do you mean IF, the "story" in We will rock you" is naff and trite and Ben Elton should be ashamed of himself.
Just shows the gullability of the British public who will flock to any old rubish.
I know it has been sucessful and made everyone a lot of money, but it does not make it good.
Some reviews here:
http://www.londontheatre.co.uk/londontheatre/r eviews/wewillrockyou02.htm
(Sorry I did not answer your question. I guess it is BEST if you have the support of the band, like Queen or Abba, as they can help promote it but not sure if it is a legal requirement).
Of course Take That signed an agreement to allow a show of Take That songs before they reformed, but after their comeback shows they refused to support the stage show. However it still went ahead as the theatre company had signed a deal with Take That.