Winks (same age 22) only has 7 more senior appearances (51) Arthur (44) has. In three seasons, and Winks has still only started 17 (3 -16/17, 8 -17/18, 6 -18/19) PL games.
Yes Barca played a 433 with Coutinho in that forward 3, but just like our format, it was fluid and Coutinho spent plenty of time dropping in to help his FB and midfield.
I mentioned Dier because, obviously, Dier would normally be the player playing in that role. Therefore it's the most viable comparison to make, and moving forward it's a choice we now have to make. I wasn't suggesting you are a champion of Dier or hold a vastly contrary opinion.
Like you, I think there are defensive compromises with Winks, but like you, I also think there are proactive gains. My point was, I think there are also defensive compromises with Dier (slow to turn, not very dynamic, not great on the press, not great when we are being pressed high).
I said in my OP, and you have echoed above, it was a brave line up tactically, and got even braver on the hour mark when we played Erikssen/Winks/Alli - but I've been calling for Poch to be braver for months. I'm not sure there's much more risk with that than any CM2 containing Dier?