If the current rankings remain intact, I can see Haye fighting Chagaev. There's just no way he will go after Boytsov. It's a 'better off with a devil you know' kind of situation. Haye's main objective at this juncture is risk minimisation.
I see it this way, UK. wins the bid, Chagaev can't fight in England, Haye will not go to Germany, so while the WBA are picking a new mandatory, Haye takes a stay active fight with Tonya Harding!!!
Have you seen Chagaev last fight? It doesn't look like he is big risk any longer - I do not know what happened, maybe hepatisis really got to him, but the point is that he looks nowhere close to the fighter he was. I think it all depends on what are Haye's real plans. If he wants to duck Wlad and sit on his belt defending it few more times, he has to fight mandatories. If he plans to retire (or fight Wlad and retire) he probably won't care about it.
Boystov is injured. So if not Chag, then Valuev or Povetkin. Further down the list you have Ustinov, Rahman, and Mormeck.
Chagaev won't get a licence to box here. The British board aren't like Texas, who'll licence anyone :yep It's not a fight anyone would want to see, I mean Chagaev went the full 12 with Skelton, who was hammered for 11 rounds and stopped by a taxi driver not long after..... and was pushed to the wire by the very average Travis Walker last time out.