As much as I loved the guy's game, he probably wasn't all that scheme diverse. He was a perfect fit for what Lebeau wanted to do on the edge, but he would have been pretty pedestrian as a 4-3 end. He would probably been effective as a DT in some 4-3 Unders and that's about it. But he wouldn't likely have been the same kind of impact guy he turned out to be.
I see Lawson as the same kind of great fit for Rex, but with some added potential to be used in other roles. If Rex pukes on his shirt and is out of here in the next year or two, Lawson could probably still be effective in 3 different roles of virtually any 4-3 you want to run. He's strong enough at the POA to play outside or inside at anywhere but the Nose and he's going to be a handful for one guy in most passpro situations. He's not likely an athletic enough closer to put up big sack numbers but I think he'll be a factor in moving QB's off their spot and forcing them into more difficult throws; which could be a boon for a dangerous Bills secondary. Setting edges upfield is likely to be his forte, but if it came down to it, kicking him inside next to Dareus could still be a great tandem to build out from.
Aside from the physical fit, I think you should give more credence to the fact that guy has great motor and really seems to take pride in winning physical battles. He's exactly the kind of ballplayer Whaley wants to stock this roster with and if he stays healthy he could spend years dominating matchups at a few different positions.