The idea of Trent as RCM reminds me of a similar conundrum with Gerrard back in the day – that seemed like obviously his best position in theory, yet almost no manager played him there for any significant stretch. For Rafa he was mainly an attacking RW in a 4-2-3-1, then a #10, a double-pivot CM in some games (like Istanbul 1st half), anything but an RCM in a 4-3-3. For England I also don't recall him there on a regular basis and of course later in his career under Rodgers Gerrard became a full-time #6.
The thing with Trent as RCM is that I don't recall any midfielder under Klopp who played this position the way Trent would likely play it. He is not a Henderson or a Gini or a Milner. A Klopp RCM is someone who will make selfless runs without the ball into the spaces on the right wing, knowing that he will not receive the ball 70% of the time and then run all the way back to restore the midfield shape – this is what Slogoszlai does now and what Elliott also tries to do (with similar willingness, but less mobility). I think Macca or Jones could play this role as well. You can't ask Trent to be that player – and it doesn't make too much sense anyway, you want him on the ball as much as possible, not off it. Maybe Naby or Gundogan in his Dortmund days would be the closest analogy to the role Trent might play in midfield, but you have to think very carefully about the overall balance to make that work.
I just rewatched the first 70 minutes (up to 3:0) of the Brentford game focusing mainly on Trent and to be honest I think he had a good game – the mistake with Mbuemo's chance had nothing to do with the position (if Robbo was fit, he would be the one left behind on the attacking set play) and his passing and chance creation was exceptional. He also stayed wide more often than not, almost "babysitting" Matip (in a sense that unlike Konate Joel needs someone with more pace alongside him). I blocked off Luton and Toulouse from my memory already, but in this game I don't have any major gripes with Trent's position or role as it allowed us to create chances consistently against a low block and directly led to the first goal. I think Szoboszlai and Gakpo both stayed a bit more central to help out Endo, respecting Brentford's threat on the counter – if we needed to be more expansive they could both have easily filled that space on the flanks to allow Salah and Jota to play closer to goal.
