I am unsure what to wish for here.
If Wasps could get the same Christian Wade from 4-5 years ago, then of course sign him up. But a lot has happened since then.
He fell out of love with rugby, changed his body shape, his fitness & his skill set for a very different game!
He has got married to an American, he has set up a business in America.
I am not sure what all of that will do for his rugby game. He would have to work very hard on his skill set, tackling, rucking, fielding kicks etc, plus his fitness has been based around short sharp intervals of effort, not multi-phase continuous defence or attack. I am sure he could do it, but will he want to? With budgets tight, he would have to be on peanuts compared to his NFL salary, not much of an incentive!
As others have mentioned, even if the Wadey from 5 years ago was available, the Wasps of 5 years ago has disappeared ! How would he cope in a game where he will hardly see the ball?
I am dubious that Wasps will want him, given all of that, as I was dubious he would make it in the NFL, but if there is budget & he shows how much he wants it, it could work.