The price would have to be right for sure but there are many good reasons to consider Holt. Playing on grass will help him prolong his career for one thing. In terms of the offense, whatever speed he may have lost is offset by how good of a route runner that he is. That trait is paramount to Warner's game and Holt may not be fast anymore but he's still quick.
It's nice to think of a burner stretching the defense down the field but the pass protection hasn't consistently held long enough for a deep threat to really be a focus. I think it would be better to have a receiver like Holt who can get off the line quickly, be on the same page as the QB in reading the coverage and keeping the chains moving.
Pace has lobbied for Holt to go to Chicago with him but I can't imagine most WR's choosing a frigid environment over a place like Arizona. With the Warner/Holt connection, NFC West familiarity angle and a speedy slot, Hines Ward-type receiving(not blocking) option, it wouldn't surprise me too much if this happened.
I'm certainly a sentimental fan when it comes to certain players and as much as I think Boldin should stay, his health is becoming a problem and certainly forces the Cardinals to be hesitant in giving him a huge pay raise. There's no arguing how dominant he can be when healthy but there's no denying that he missed 8 games the last two years and came up lame after the 1st playoff game.
As great as he is, he just can't seem to stay on the field. When he is there, he's often at a greatly reduced capacity. If the Cardinals get a 1st & 3rd or something along those lines, I think most fans will be able to appreciate the move fairly quickly since I think he's going to continue to be pretty dinged up over the next couple of years and on the decline.
I'm worried about Doucet since I have no idea why his progress has been so slow. Maybe Whis is just taking it nice a slow on purpose but I really thought he'd have seen the field much more than he did last year. If there's nothing wrong with him though, I think the receiving corps will be "fine" without Boldin. If the trade-off is a better(dare I hope, "good") running game and maybe Holt added to the mix? I say get it done.