It would be a great help when you add reads and dynamics what were going on.

If one of them would look on this situation and have same approach as you have,thinking that AA vs AA vs his hand and willing to put 500bb in the middle with hand like KQJTds then you pretty much flipping for 500bb. not sure its a great idea.

the cold 4bettor is the most likely to have AA and when I only call I don't have AA almost never... so the 3bettor don't expect me to have AA and I expect him to call with all hands to play the hand preflop and only going allin pre with AA, so when calling if they go allin preflop I expect them to have both AA pre most of the time! That my thinking about the situation but not has to be correct, maybe I'm wrong xD

I would have liked this more if you raised UTG instead of isolating a perceived weaker player(?) but I still believe your thinking is spot on, i.e that BU will call all his non AA hands which will work out quite nicely for you. And of course jam his AA hands, in which case I think you gladly should take high variance play and get it in.