It's similar as to why I wasn't really fussed as to losing Lukaku, if for stupid money. The way we've set up for well over a decade simply didn't suit him, and it was responsible for every bad patch of form we had because suddenly we didn't look like we'd get a shot on goal ever when the ball permanently ping ponged off his shins.
But with a Mata in a number 10 role? Perhaps Barkley deeper, alongside a deep lying playmaker in Witsel? Different ball game - suddenly Lukaku is indispensible.
If we keep Rom and he is fully committed to the cause we could be outstanding going forward next term.
My biggest reason to like Koeman last season btw was his ability to change his set-up and tactics on a game by game basis depending on the oppo.
So I doubt we'll see too many games where it is a 'rigid' system - so suddenly a player like Mata - with experience of playing anywhere across the attacking mid slots and the ability he has will make him the key cog in our team - the fulcrum if you will, whether he's on the wing or as a 10.
That allows Ross the freedom to, as you say, play deeper when needed, or have the space he needs to operate to his full potential in the No.10 role.
Watch clips of Martinez's first season. Most of Ross's best moments that season came when he had Pienaar next to him, operating from the left but drifting everywhere to link the play.
If this signing comes off it'll be superb for the team and the club as a whole. Throw in Witsel and it's a massive statement that yes, even if we have underachieved and we may still have to sell one of our better players, we mean business.