I wouldn't mind it. In certain situations he'd be a #1 for us. Outside of that, he'd be #4 or 5.
But tell me who on our WR core would you want to catch a 3rd and 3 more than Boldin?
Fitz would be the only one I'd put up there with him, and I'd give Boldin the edge due to superior strength and toughness. Another blocker as well. That would give us three good blocking WR's and redundancy in case Fitz or Floyd got injured.
I think he'd accept the role. He's older. He has a ring. He's had Colin Kaepernick throwing to him the last few years. Or more accurately, not seeing him being wide open... or badly missing him.
We could definitely find a spot for a guy like him. We also have to remember two of the guys above him, or at least one, are rail thin speedsters.
Rod Graves got rid of him, not SK. I would focus on our needs first, but if he's still there after we address them, or if the guys who could fill those needs are gone. Then yes, he'd be a wise pick up.
It's about matchups and situations. Boldin can be very useful, and I think that's what people are forgetting. They are applying the usual starter base role for him. That's an error. Utilize his strengths in certain matchups and situations and he would be another weapon for us, especially in the clutch where it matters most.