I think teams like Chelsea have to be pressed, because they are very comfortable on the ball. Mind you, I agree that Wembley is a big park, so this is a tactic that I would use at key moments of the game, rather than as a blanket tactic.
It's a tactic that works if, like Barca, you don't make a habit of giving the ball away cheaply. I understand that our pacy, counter-attacking tactics necessitate a degree of risky, speculative passing. However, there's a difference between speculative, and just plain inaccurate. Too much of our possession is wasted needlessly, in poor inaccurate passing, IMO.
Isn't the WHL pitch quite big, considering we do have Bale and Lennon, so the groundsmen try to make it as wide as possible. What is the difference in dimensions between WHL and Wembley? Also, I think pressing the opposition like that would work especially well against the lower teams that like to "play football", like Swansea, Wigan and even Bolton (under OC). This is because the pressure is more likely to force their players into mistakes. With the better teams, Man Utd, City, Arsenal etc... their players make fewer mistakes, and so pressing them might not be as productive.
Some teams do very little pressing, especially those set up to counter-attack at pace and nick low scoring wins, I believe. They set up with two banks of four, often with a man sweeping up between them and invite teams out, leaving space for their attackers to use when they get possession. Most sides have a balance and we really played quite an extreme example of pressing against Swansea.
We're not strong enough defensively though Lidls, especially on set-pieces. We seemed to try that tactic against Arsenal and it backfired horribly.
In the case of Arsenal, you need to press them higher up the pitch - in their final third, catching them between playing it out of defence and looking for options in midfield. Once it gets beyond the halfway line, they have more momentum to their passing moves.
"I'm still convinced that we concede far too much possession, needlessly..." That's my feeling: but only against teams that press. It seems to me when teams press us, we ought to react by playing more conservatively, even backpassing frequently, because that will make them run out of steam, and make it more likely to find a way through them. Instead I see the same high risk passing which works when we have time and space, but which tends to give the ball away under pressure. As for pressing, it seems like there's a general agreement that we should do it only when appropriate, but we don't have the squad to do it all the time. So that sounds like a plan. Everyone must realize the run in is likely to come down to who works harder.