Well they do have a few of their own FAs to pay
Gotta save 3-5 for in season
Draft picks
Depth guys
So basically Forte is the only notable FA? That's not Revis.
I think we all understand where you're coming from in terms of reminding people about in-season signings, incentives that may be reached, draft picks, etc---but those can be manipulated by making a move at that specific moment. We've got some smart people managing the cap, so I'm sure Belichick is well versed in these exercises.
In other words, there are MANY ways to free up cap space, whether that's restructuring Amendola, cutting guys like Cannon, LaFell, extending either Jones or Hightower etc, so at the moment 15m dollars (approx. after the cap increases again) is a
fine position to be in. One way or the other, the Patriots are going to free up additional money. They haven't even really gotten started yet! The only thing that happened was someone retiring.
I share some of your concern about signing a guy like Forte to more than a 1-2 yr deal, and I also feel as though his pricetag may prevent us from bringing him here, but he's definitely someone who should be explored under the right circumstances. The same logic would apply to another "over the hill dinosaur" in Anquan Boldin, who still caught 70 balls this year and would be a fine candidate to contribute as a possession/over the middle type of receiver for a year or two.
These types of veteran/value signings have been one of the bigger reasons why we've been so successful over the long haul, although as you mention, one must be cautious when doling out big bucks to older players. I just don't see that applying to this situation, that's all.