We already have one of the best #6's in the league.....
Both he and the CBs are all we leave back, if an oppo has transitioned against these 3 we are limited to its effectiveness, this is how we have chosen to play. BUT we can affect the oppo by not allowing that transition to build, this is where a better, more aggressive and cunter #8 comes in (BTW I think Bentancur is actually got a lot of the attributes I'm looking for here, he's better than Sarr on the ball and he's more aggressive than him too, I'm not sure he has Sarr's legs to get up and down the pitch and provide 3rd man runs behind oppo but I'd start him ahead of Sarr in a heartbeat).
By the end of last season, Kulu was playing as a Centre Forward or false 9 and we were better for it.
Again, this isn't saying we shouldn't get better wingers, we absolutely should, I also think the Club acknowledges this as to why Werner is on loan and not permanent. All I'm trying to articulate is where can we make our biggest improvement, and having got Solanke we've fixed a huge number of areas upfront with just one hire (this isn't the end but it should have a huge uptick for us both with and without the ball) the other big area dealing with our biggest weakness, putting Rodri in as #6 wouldn't change things, he will still be dealing with multiple transitions with just him and 2 CB's, but having a player in front to snuff or disrupt oppo transitions before they begin is transformative, and will prevent 10-15 gaols against us (being able to defend and score from set-pieces is also right up there too).
Solanke improves our press, which also improves our defence but because of how we commit numbers forward I'm convinced we go a very long way to addressing our biggest weakness which in turn means has the biggest impact on us winning more games.
It doesn't mean in any way I don't want a dribbly winger, I absolutely do but I don't think it has as big an impact/transformative on our performances as getting a better #8 than Sarr (and I stress I love Sarr).