Tomiyasu is a brilliant player but I still don't consider him a full back. He does a job there because he's smart and ambidextrous but his strengths aren't in attack but in defence, his final ball isn't good enough for the role.
If we want to keep playing him there we need to find some sort of Theo-Sagna type of partnership on our right flank, which could actually work if we played Pepe there and moved Saka to the other wing. If we insist on Saka as a RW we have to get a more attacking RB in, and Tomiyasu either rides the bench or displaces White as our RCB. Very early days of course but Norton-Cuffy looks a lot more like the type of right back we'd need behind someone like Saka