Yeah he doesn't need a system. He's better than Mctominay in any system. Better tackler and shows for the ball much more.
He's a fantastic give and go player that we need to beat the press. If Frenkie doesn't come then I want to see him play with Fred. They'll be a great pivot and way better than Mcfred
Donny does need a system tbf. In the right system he can be excellent. In a no system you'll find a lot of better players because they are quicker, stronger, or better dribblers/passers. Donny is an allround player with a lot of qualities that can gel in perfectly in a well drilled team. Great teams needs players like this. You don't have a great team with 11 superstars.
Concerning the never ending debate about his position, Ten Hag has called it already that he's a #10. All these people calling for #6.. at that position he'll be decent at best. He played there for Ajax only a few times and was never great. He can do a decent job there, but you can find many better players there. Donny can be an excellent #10 however, also in PL. However a very different #10 compared to Bruno (or Eriksen). Donny is not that creative. But in and around the box he's very dangerous and he's very dangerous in link-up play.
However it will be difficult for him to get into the team. Whether he'll be successful depend on with what type of #10 Ten Hag will play. If he plays with a playmaking/creative #10, Bruno and Eriksen are simply way ahead of Donny. However if he wants to play with a #10 that's on the move all the time, displacing the defensive unit and being at the right place at the right time around the opponents box, than EtH knows that Donny is his man.
So far it looks like it'll be the option with Bruno on #10, however this is also knowing that Ten Hag hasn't been able to work with every player that he desires. The whole setup might look completely different with De Jong and Eriksen added to the squad. If De Jong and Eriksen end up the two in front of defense, then Donny could be a more logical option on #10 than Bruno, as he offers other qualities that provide more balance on the midfield.
---- Eriksen ----- De Jong
Sancho --- Donny --- Bruno
---- Martial / Rashford ---
I think this could very well be what Ten Hag is aiming towards. It may not look like it right now, but that's because Ten Hag thinks in concepts and De Jong is a crucial part of his concept. The more I think about it, De Jong coming in could have huge implications for Donny as well.