I would love to get Norwell, but I don't think an OL qualifies as "blockbuster," although he would be the best addition, IMO. I think "blockbuster" has to be a good name, and per the OP, one that would also help.
The following might fit that criteria:
1. DJ Metcalf. not sure how we'd get him, (Davis and a 2nd?), but man, that would be something.
2. D. Cook (RB). Yeah, he is oft-injured, and the price is ridiculous, but he'd up the running game. The OL is bad, but not the sole reason. We have 2 backup RB's rotating as starters.
3. K. Mack or DE. Hunter. Pass rush upgrade would put the D on another level.