I agree that the XP system is a failure. And on top of the failings of the system it just sucks to use. 1 point at a time for 50+ players is tedious as heck. And while I don't mind the ability to "upgrade" a player's DEV level it seems kind of contrived to me.
I miss the progression system specifically because of the cap/ceiling it placed on player development. Where I hated it, and the XP system for that matter, is the idea that you can "know" a player's potential or development level immediately. Either once they are drafted and signed, or before hand by scouting it.
I don't get the idea behind this player got x stat this and y stat that so he should be rated higher - makes no sense to me.
However, I see a way within what EA has in the game right now to fix it. The PROD rating dynamically changing based on the stats within the season. The season PROD rating would fluctuate dependent upon the stats you accrue. During the season your PROD number would be reflective of where the player ranks in significant stat categories - with some being more heavily weighed than others. The season PROD number would be calculated into OVR. During the offseason the last year's PROD number would be used. Legacy - is already in the game and should be referenced for career production/success.
Then you take the PROD/DUR/PHYS/SIZE/INT ratings and average them out for the OVR rating. This adds in injury concerns and to some degree scheme fit into player's OVR rating. Now when you have a 57 rated WR that you amass 35 receptions for 675 yards and 9 TDs with - his PROD number is going to drive up his OVR rating - nothing has changed - meaning without awarding a single XP his OVR would change based on his production - his skills would all be the same (until you award the XP).
Now when it comes time to sign that player - he is going to be looking for over the league minimum and likely looking for some bonus money - where as in the past he was rated 57 so he would sign for like 650K and 1 year - and because you clearly did not need his XP to get him those stats - you don't ever award them so you keep this guy on the cheap. But if PROD factors into OVR, and it should be the most heavily weighted in the formula, then all of sudden you have to pay more in line with his stats than his arbitrary ratings.
Players in real life - they have a ceiling. See David Carr/Joey Harrington/Robert Gallery. Heck look at A.J. Hawk - 5th overall pick in 2006 by the Packers. No matter how many stats he gets he will never be faster, quicker, able to jump higher. He can work on techniques - tackling, block shedding, and study tape to increase his play recognition and so forth, but he will never be a HOFer, he is a solid productive player, but nothing special. He is likely as good now as he will ever be. I do not see how a system that replicated that was a bad thing...
Having PROD be stat driven within seasons, leaving legacy for whatever that is for, and dynamically factoring PROD into OVR along with a potential based progression system while hiding the POT rating seems like the most authentic way of simulating what goes on in the actual NFL. At least, in my opinion.