Squads have limits, and the best squads are very finely balanced. When that balance is thrown out it can be a detrimental thing.
Dempsey plays virtually when fit. Sigurdsson is currently trying to earn his spot on the roster. We have Holtby to add to the mix. That to me shows a lot of strength in depth.
Sneijder would be an instant 100% guaranteed starter. He wouldnt have to earn his spot, its a given. If thats the case, what happens to the 3 we already have? He wouldnt be rotated in and out, he wouldnt be played out of position - not a player of that calibre and cost. So the others would be the ones to compromise.
So the team imediately is stronger, no question, but what about the long term when these players jump ship for regular football? What of the squad? Flexibility in selection/rotation?
Once again, I reiterate, Im not saying dont sign Sneijder, or that he wouldnt improve the side. Im simply saying there is a concern for me about wider implications.
The link posted in the Independant to Willian, however, stacks up much better - introduce a player that covers either wing as well as the AM position? Thats makes a lot of sense for the team and squad IMO, his flexibility means he offers cover to players and competition rather than simply ousting them to the bench.
I'm not gunning for his signing, I think his wage demands will be too much, I'm just saying your argument of "Don't sign this good player because we have loads of worse players instead" is flawed..