Maddison played an 8 at Leicester, but was the one with the license to get forward.
His Celtic system had the 6 do all the dirty work, and collect the ball from the centre halves to move it foward, and then two 8's. One was to get around the pitch and move the ball, pick up space and hound others, the other was to advance more.
I actually think we already have the perfect blend for that. Bentancur and Bissouma are both capable of playing 6 or the first 8. Maddison is the advanced 8. We need another signing in there to cover the 8's. Alex Scott would be my choice. He can play both types of 8, and would be learning off Maddison daily.
Full backs is the issue - Porro and Udogie are more suited to a wing back system, which isn't going to happen. Udogie is youn enough to be trained into it. Porro I think can learn it, but it'll take time. Emerson needs to be kept.