[Formula 1] Can a independent team win the WCC?

All this talk of Schumy and Brawn buying Toro Rosso has got me thinking about whether or not an independent team win the constructors championship. I know in the past teams like Williams thrived, but it seems F1 budgets have begun to soar higher and higher. I can't see how a team could win without a major auto company backing them.

Even if you put money aside, and look at teams like RBR and Spyker and STR they all buy their engines. This gives them a really powerful engine they could never produce themselves, and a bunch of development time for other things such as Aero. On top of that customer engine programs even add more to reliability because the teams can use telemetry and engine data from their customers as well. However, lets say Spyker became a top team, I can't imagine ferrari would supply them with engines the next year because they are a threat. Am I wrong? So even if an independent team developed a winning car, they would then have to allocate resources to an engine program which would hurt car development in the following years (i think).

So I'm trying to figure out how Schumy and Brawn would want to buy a team knowing they could never really compete for the WCC. I had a wild idea though, what if they bought STR and then brough VAG in. A similar type of deal as BMW Williams in the past, without all the bickering and blame on the other half of the team. Then you would have enormous VAG with brands like Porsche, Audi, Lambo, Buggatti, VW all backing this new Schumy/Brawn run team. Schumy is german and extremely analytical so the relationship with a german automaker could be successfull. Plus VAG would then have a pretty strong entry into F1, with a much better outlook then Toyota. I don't know enough about Formula 1 to know if this is the dumbest idea and it's impossible, and I'm not trying to act like i'm some genious, but could this ever work. I just feel like that team could be insane. Plus many of the people who were part of the Ferrari Dream team could be pulled to the new Brawn/Schumy team because of their longstanding relationships and Michael's ability to earn the teams respect.

Just an interesting thought, I would love to hear what you guys think about this.