Although this is a very good discussion (and AB's cap analysis is as always a joy to read), I think we're mixing up various issues together and getting confused. As I see it there are two sides of the story:
1. Players we could get via FA this year vs taking care of our important homegrown guys from 2014 and beyond.
That for me is a dead end strategy, and I agree with those who say that there's no way we should risk losing someone like Kaep, Crabs, Iupati etc for bringing in a big name FA who will require a multiyear lucrative deal. Our cap just can't handle it. So that for me rules out names like Bowe etc. I highly doubt we will get any big name FAs this (or next) year.
2. Players we could acquire via a trade, possibly as a 1-year rental
I.e Harvin or Revis.
That's a completely different story and one that I think we should consider. In fact a big name via a trade is the only scenario we should consider. We are packed with talent, but those who think it's easy to get back to (much less win) a SB are deluding themselves. The rest of the league doesn't stay still, either in designing schemes against our team (see how our D was less effective compared with last year - injuries can only explain so much) or in acquiring talent of their own. They are not idiots. If we want to add a championship we need to up the ante. But we can't do it via a big FA spree as the cap won't allow it. However a trade is another story. We have plenty of ammo to pull it off (13 picks plus Smith either himself or as more picks that we might get out of a trade). Yes, it's a win now strategy a la 1994. What was so wrong with 1994? We got the ring and stayed competitive for years after.
Of the two, Revis would be the one to go for if we can swing it. I think we can handle his remaining salary from the Jets in our cap and he can help the team now in a position of great need. It's only going to be a 1-year thing, i.e. at the end he's an FA and can go get his money from someone else, hopefully after having a ring in his possession and having demonstrated to the league that he's fully healed. The injury is why I think he will not be a distraction, much less hold out for a multi year deal. Playing for a championship calibre team and getting his freedom in the end after marketing his skills to everyone is incentive enough.
Harvin can also help immediately, and in two positions of need. But I'm worried about any kind of head injury history and he might be someone to cause static in order to cajole the team into giving him a multi year deal - which we can't afford as we said.