I like a lot that idea.
It's like in wargames : you have (for example) 1000 points to build your army. You can pick 5 big monsters for 200pts each, or a big gobs squad, 50figs for 20pts each. It allows the player to make a very personal approach in his squad building.
It's also -I think- a good way to balance the game. If you're not a really good tweaker, you can build a very strong line...but you'll certainly have weakness on your back field. But you'll be able to defend and protect your QB, allowing you more options than having a weak team on a classic weight limit. Like in the real world. Even weak teams always stills have good elements.
Concerning football, you can build a strong line including a TE dedicated to protection, or big FB, or fast light weight TE and monster linemen, one big nose tackle and DT to stop power runs, etc, etc...
I think I'll try that weight system in my own rules soon (= when I'll fix my board
). Perhaps I'll experiment multiple weight limits (one for linemen, one for skills players, for example).