Instead of having an "ideal weight" at a position that all players trend towards, I think that players should just have certain body types that they can't change (drastically) from. Eddie Lacy is never going to look like Ameer Abdullah, but that's okay because they're different types of backs. I'm also noticing a lot of discussion on 3-4 defenses, where some people simply leave players as DTs and slot them into the DE on their depth charts. We shouldn't have to do this. There should be more 300+ lb DEs and 3-4 coaches should target them. Draft's should also have nose tackle body types. There should be some wide receivers at 5'11" 200 lbs and some 6'1" and 235 lbs. Some linebackers should be less than 250 and some should push 280, and all this variation shouldn't just directly correlate to height. Let there be short, heavy guys, and tall lanky guys.

Absolutely. Would be great.
Like suggested in another thread (by someone else), we, as GMs could also set a desired weight for the player to match. Better : the player would not automatically reach that wieght, or will fluctuate around it. Like Lacy...uh...pehaps not that much :)

i agree there should be a limit to how much weight can vary, for instance in real life a CB and MLB have completely different styles not just in play but also build
CB - usually tall and somewhat lanky, built for sustained speed and quick acceleration
MLB - average or slightly above height with a stocky build, builds differ depending on play style
---Generalized - taller a little less stocky good speed average acceleration (mainly for run stopping within a couple yards and short-medium mid-field zone/man, usually not that great at blitzing or tackling for a loss)
---Blitzer/Run Stopper - shorter and stockier, with more strength, explosive acceleration and average speed (mainly for crashing the line either to blitz the middle after the QB or stop the run at or behind the line, not usually the best pass defender though)

also with most LBs/TEs/FBs/OLs/DLs the extra weight is muscle and muscle weight is almost impossible to lose unless you just quit working out at all then it turns to fat which you then have to lose

I like the idea of being able to set a desired weight of a player on your team and depending on their discipline it would determine if they can achieve it. Would be a cool add on

All great comments / ideas in my opinion.

Exactly right. The lower your BMI, the harder it is to lose or gain weight. A big 'ol boy like Vince Wilfork could drop twenty pounds very quickly and it wouldn't even be that high of a percentage of his bodyweight.