About Messi playing as a attacking midfielder/play-maker, that is something that the whole world knows. It is not just my saying. Ever since Iniesta moved out from Barcelona, Leo took over his duty. He is no more considered as a RW. I have seen in this forum many different line-ups with some of them ( as yours ) placing him at the RW position. That is wrong. You can put him anywhere you want, because he is so versatile, but the reality is that the right flank will stay open. Now. I am not 100% sure if Trincao will be the starter there ( I wish he is ) because if Dembele is fit and ready to play, Setien may start him ahead of the Portuguese. That is fine.
To be honest, I am not that much against Martinez, as you may think. I would prefer him over Neymar, Griezmann, Coutinho and Dembele. That should tell you a lot. I am just against the idea of paying 111 m. for him with all our limited resources at the moment. With that money we can buy 2 solid pieces for our defense and midfield.
Thats the most reasonable post I ever saw you write, thanks for that.
On topic: you are obviously right about Messi, everyone knows hes nominally not a RW anymore, the question is where do you play him? There are 3 options (unless you have more ideas):
1) LW - Suarez - Messi
2) Double-Pivot with Messi as #10
3) LF - Messi -RF
Option #1 is what we do right now (which means sacrificing our right wing). Riordon (and others) advocate that, get a good LW and maybe play Griezmann in the center. Fine by me.
Option #2 requires 2 very good wingers (maybe Trincao is one, he looks very decent) and probably another defensive midfielder. I dont think thats a pragmatic approach, and personally I am not a big fan of the midfield structure in a 4-2-3-1. Its wing heavy, which is not how I see Barcelona.
Option #3 is my favourite, especially since I dont see Griezmann succeed here in another role. And I guess LFs/RFs are preferable to wingers in that formation. Messi is not at his best in the center anymore so ideally you want 2 mobile forwards, who target the CBs (instead of FBs). No idea if that can work out, but with Trincao, Fati, Dembele we could easily revert back to option #1. Thats my whole argument. Plus we need a CF sooner or later anyway.
Some people would rather get Haaland, which I cant argue against, but he seems to prefer the PL/Madrid (just a feeling). I have little doubt in Lautaro though, he was the only forward we played this season who looked dangerous throughout the game (and thats special for me). But goal stats are the easier scouting I guess.
As for improving our defense/midfield first: I wouldnt mind that, ideally we need a quality transfer in each line. But for me those issues are all roughly equal and the Lautaro option presents itself. Finding a clear cut impovement for midfield/defense is harder, and just as expensive. And yeah, I agree, 111ME for Lautaro would be excessive, but 60ME+players kind of sound reasonable. We will see whats possible this window though.