Hardy is very very unlikely.
Bennett on the other hand, is real possibility. He had a good season with Tampa and looked for a big deal last year but couldn't get it. So he took 1 year deal to play in Seattle. And remember, he is in a rotation there. Seattle has a ton of pass rushers. Cliff Avril, Bruce Irvin were used as OLB's and they had Bennett play the 5 technique on some plays and OLB on passing downs. Chris Clemons and Red Bryant often times played the 5T and pulled Bennett out. If you don't know how a 3-4 works, the DE's are more like DT's and inside pass rushers while the 2 OLB's tend to rush the passer off the edge. Sometimes you rush the 5 lineman. However in some plays an OLB will drop in coverage and that DE will put his hand down and rush from the edge. Seattle mixes it up as well as anyone. But snaps are distributed so Bennett wasn't an every down player. His production per snap is very good.
For what is worth, PFF put Bennett as a 4-3 DE and he was ranked 5th in the NFL this year. Hardy was ranked 3rd.
To give an idea of playing time... Bennett 617 snaps, Hardy 891.. Jared Allen, Ninkovich, Chandler Jones had over 1000 snaps. Most full time players over 800.
So the average joe will see 8.5 sacks and say.. oh OK, he's good but not great. Not paying attention to his high run defense scores and limited snaps. Bennett might be every bit as good as Hardy at a cheaper price. And he's Martellus's brother, so hoping they get this done. He could help.