We have to consider the way we currently play, our midfielders dont really get much of the ball to creatve too much, or dictate our tempo.
Dyche system just uses them as runners / blockers and to hold shape.
I would say he is wasted in this system and we could get a much less gifted player and would not see too much of a drop off.
Some of his Belgium games he looks a completely different players, and I would expect him to be unreal in a team that lets is midfielders get on the ball.
Add his size, and pace into it too and you have a player that ticks every single box, he could go right ot the top, easily.
Fans wont see past what they see on the pitch, and thats fine - but their is a much much bigger picture, and Onana is linked with everyone of the big boys.