I'll advocate just a little for Forte.
First, I thought he was cut by the Bears, but that was wrong. I would agree that as an UFA he would be less of a target.
I'm sure the team is hoping Lacy will come back in better shape, but other than it being a contract year and hoping he listened, what makes anyone think he'll be more diligent this year. He's showed up out of shape each year, but each year has been worse. Is he now suddenly going to get it done because he's been called out. I say, send a message. Forte is a message, but if you prefer, draft one early. Either way, I don't want to depend on Lacy's commitment because to date, there hasn't been one.
As for Cobb and Monty, I kind of disagree Salmar. They are not filling the receiving RB role. They fill a niche role in a gimmick personnel grouping. Not necessarily a bad gimmick, but still a gimmick. With MM wanting to play up-tempo, when Cobb or Monty are in the game without a RB you really don't have a running game for the whole series. You can do that a couple of series a game but it's a gimmick since you aren't actually gonna run those guys between the tackles more than once or twice.
Forte isn't just a motionless target sort of guy. A creative coach could find ways to use him that might partly mitigate the lack of a TE. In a 2-back alignment with a FB you can run power, you can put Forte in motion or in the slot like a TE and isolate him on a LB or force a S into the box. You can't do anything like that with Lacy or Starks - they don't have the skills.
He'll probably be too pricey and TT doesn't usually look at UFA's to much, but this is exactly the sort of veteran signing that teams like the Pats and Broncos make to add to their teams. Yah, there is a little risk, but I still would not be opposed.