Interceptions are indeed out of control. I understand I built my defense around them but that's because it's silly to fight the sim rather than go with its strengths.
Top of my head, not yet well thought out, I like:
Pro-offense: make interceptions significantly harder to get in single coverage. I'd like to see a roughly 20-30% drop in interceptions with the builds that currently exist.
Pro-defense: improve run defense and screen reads for players in zone defense, including defensive linemen in the flats. the fact that 70+ vision players are constantly oblivious to runs or screens coming right at them is insane.
improve defense ability to recover forced fumbles
If we could have more complex changes, I would ask for QB decision making to scale way better with vision, so that you could choose to build a lower throw/str but higher vision QB that would make better decisions but just didn't have an amazing arm. But that requires the *game* to correctly calculate the "right" decision every time and I think that's probably ridiculously difficult. I'd also love to see smarter pursuit angles on outside screens and runs from defenders, maybe even a slider defining if they tend to do aggressive pursuit or safe pursuit. But again, that requires the AI to be able to forecast what path is actually best and then determine if the player passes his vision check to indeed take the best path, and I think refining the "best path" logic is probably insanely difficult.
I'd also selfishly want defenders in zone coverage to have a backup zone...probably automatic, but i guess it could be user-chosen...where they would go if no one was in or immediately headed to their zone.
I actually feel that the balance between O and D is about right, and would want for the nerf in interceptions to be large enough to counter any benefits given to the defense. The fact that I think the balance is good could lead to the "is it broken?" question, but at its core this game is meant to emulate football - a large part of the userbase enjoys the actual physical sport and would prefer a game that mirrors that better. Can you simply learn to play within the current parameters? Of course (well, at least Ryan can

). But I think the suggestions I have made would preserve the balance but make the game "make sense" to more people where they would feel more like it represented an actual football game, and less like a computer game with its own set of rules.