How exactly is it weakening the squad? Brown is fit, rarely plays, Hargreaves hasn't played for 2 and a bit years, Scholes is probably retiring... How exactly are we losing 3-4 players for one signing? We then have a keeper coming in that will be on less then VDS... The side isn't weakening for the sake of facilitating one player, its evolving to encompass new players.
Brown: has a replacement.
Hargreaves: doesn't have a replacement, but it wouldn't be out of the norm to bring a young player up given that anything would be an improvement over his contribution for 2 and a bit years.
Scholes: Needs to be replaced if he is indeed retiring
VDS: Replacement on the cards
PIG: already replaced
There's 300k in players take 50-75k away for a replacement keeper, and you have nearly 75-85% of your proposed wages but even then I'm sure there are ways around the taxing issue. Whats stop Mr. Sneijder for example to say he lives in Spain, and lives in a club provided house when playing for United? F1 drivers "live" in Switzerland yet work for British owned companies and are not required to pay the full english tax percentage, only in their country of choice.
In regards to player matching clause, whats stopping United from paying sponsors to pay the players? I believe this is common practice in salary capped competitions. This isn't just about United of course but any club....
Fergie will buy whoever he likes regardless of what you believe. If he says this player will be key to success then they'll buy that player based on the belief that by not doing so it will be detrimental to potential future success. He won't have a blank check, but hands will not be tied for potential signings either.