One thing I don't quite understand, is that I've read Jonathan Wilson mention in an article last week that Van Gaal's preferred system is the 4-3-3 (or variant of it). I know he went with the 3-5-2 with the Netherlands at the World Cup due to the players available to him, but why did he have to stick with it with the Mancs? Unlike with the national team, the personnel quality problem is one that can generally be solved by money, which means he could've just stuck with a 4-3-3 or whatever he preferred in the pre-season while pushing for the new CB knight in shiny armor to arrive, instead of trying to convert the team to play a new way.
It'd make sense to cut the coat according to the cloth if you were sure you weren't going to get the upgrade you need. Otherwise, why introduce more complexity into a new job? Are they really having problems attracting a couple of new CBs or are there some spending limits they're bumping up against?