I'd sign Disasi if he was reasonably priced, and play him at centre-half. I'd be happy enough to take another loan deal on either or both of the other two, but huge wages plus transfer fee would be too much, IMO.
I thought Emery would have used Desasi a lot more with Konsa at RB, it does make us much more solid, but for some reason he is out of favour.
When we signed Disasi, Mings had been out for a year and a half and we were getting a defender injured literally every game. He probably, quite reasonably, didn't expect Mings to be as good as he has, and also wouldn't have anticipated that we would undergo our best period without a defensive injury in years. Touch wood, fingers crossed, etc.