Adding grit/size is not the issue.
It is adding guys who don't have enough skill to be in the lineup if they didn't have the size/grit, or sacrificing skill for the sake of grit.
For example, if Coleman and Goodrow were not "physical" players, they'd still be very good players. The physical element helps elevate their game, but they would find ways to impact the game even if the physical element wasn't used. They are skilled players too. They were better players than the physical players they replaced in Tampa's lineup (Adam Erne and Ryan Callahan namely). Even Pat Maroon, who is probably the least skilled grit they have, is still good enough to play on the 2PP. Simmonds has lost that role because we've found better players.
Thornton, Foligno, Simmonds are effectively useless when they don't use their size. That is the problem. No amount of grit/size will make up for a lack of skill and the inability to take a regular shift. The kind of grit guys you need to target are the ones who work hard and have enough skill to make their grit useful. Blackwell works in that way. Knies. Hyman. Bunting. Joey Anderson. Or heck even Curtis Douglas may be able to be that guy at some point.
Effectively, it is time for Simmonds to be relegated to the extra forward role permanently. Clifford should never take another shift for this team. And Spezza should get one more cheap contract so he can get to 1000 points, but it may be time for him for him to be on the outside as well. It is time we start relying on guys with energy AND skill... And can reliably play 12 minutes on any given night.