OK, when a coach is making a defensive call, he looks at the package the offense is putting out on the field, the down, and the distance. Sometimes, other things apply like time and score.
First, let's talk about time and score. On offense, you have a choice of when to run a time consuming offense if you are ahead, or a hurry up offense when you are behind. But, for some reason, you don't have that on defense. So, if I'm up against a running team, and I choose mostly run stopping plays... when I'm ahead with 3 minutes left, and that team starts passing... they have a clear advantage. I don't have any way to choose, when I'm ahead with 3 minutes left to go in the game, a prevent style defense or at least some better pass coverage plays like a 2 or 3 deep man... If offense and defense don't have the same choices... an advantage is given. Now, maybe the AI automatically does this... I would rather have my own choices to make, rather than the AI. If the AI doesn't do this, then, again, there is a clear advantage.
I tested this by setting my Hurry Up to 10, and having 80% running on all 4 downs, but only having a couple of running plays. So, out of 40 plays, I had 32 passes and 8 runs. The defense crushed our running game early, and continued to for a while... then our Hurry Up kicked in, and we went crazy passing. Easy score after easy scored ensued, until we tied the game in the 4th quarter. Then, we were able to start running the ball. Basically, our gameplan changed twice... We started off running, our gameplan changed to a Hurry Up, then we went back to a running game. It's hard to stop this... you win either way here. If they don't stop the run, you run all over them. If they do, eventually you go to the hurry up way before it can be expected and are able to take advantage of their obvious run stopping defense...
2) This brings up my second point. Hurry Up and Slow Down should only happen in the last 2 minutes of the 2nd quarter, and in the fourth quarter. I got down 4 scores, and I was in Hurry Up in the last 5 minutes of the 2nd quarter.
3) Personnel choice. Now, the offense can choose which personnel packages they want to run. As I've mentioned elsewhere, I have taken advantage of this by running all 3+ WR packages. For the majority of teams, if not all, this removes 15-20 of their 30 defensive plays from the game. If I see a team running mostly nickel and dime defenses, then I'm going to run a ton of 2RB/1TE/2WR, 2/2/1, 1/2/2, 2/3/0, and 3/2/0 plays against them. The way I feel defense should be done, is to have a matrix with down and distance, as we currently have, but instead of choosing DB/LB stuff, we choose personnel. So the defensive matrix should be personnel, down, distance. I would like to see it where you can run a base defense against a 3WR set. If it's 2RB/3WR, then the guy who would normally cover the TE will cover the 3rd WR. If it's 1RB/1TE/3WR, then the guy who would normally cover the 2nd RB (FB), will now cover the 3rd WR. I understand that this could be difficult to program, but there would be some good blitzes that would work great against the 1/1/3 personnel that only have 2 CBs... More on the matrix and play choice in #5.
4) Not enough plays. If anything, defense should have more plays than the offense. The defense adjusts to the offense, and needs more range and variety to handle different situations. I think the defense should at LEAST have 40 plays, same as the offense. Here's an example of the issue. I have to have 4 plays that I use ONLY on 3rd and long.. one for base, one for nickel, one for dime, and one for quarter. I ONLY use this on 3rd or 4th and long. I would also use it when the offense is in Hurry Up. But that's it. So, now I only have 26 plays left to defend with. Does the offense have plays ONLY for a specific situation? No, they can use the All Go play on 1st and 10, 2nd and 1, 2nd and 21, etc. Same with most plays. Most likely, you aren't going to do a dive play in 3RB/2TE formation on 3rd and 25. But you might use it on 2nd and 12, 2nd and 1, 3rd and 1, 1st and 10... There aren't plays that will be specifically used for one situation on offense, but there can be on defense. Which further limits the playcalling breadth needed to defend against a diversified opponent. This is why I say the defense should have MORE plays. But, the defense, to keep balance, should have at least as many plays as the offense. 40 is reasonable, 50 is better ;)
5) So, a coach basically looks at 3 things to determine which play to use... personnel, down, distance. On defense, we don't have the personnel choice in our matrix. We have down, distance, and a basic play combo between the DBs and LBs. I don't have any choice of what my defensive line does... Overall, this doesn't allow to be able to make good play calls. Within the 1 deep man DB play call, there are many different possibilities. Some I WANT on 3rd and short... some I DO NOT want. The way the gameplanning is on defense is too generic, and allows too many opportunities for bad situational play calls. So, to gameplan, you start out by choosing the personnel package you want. I don't know how the plays or the game engine work, so I can only guess how this would be set up... I don't think you want a matrix for each of the 10 different offensive personnel groups... I would like that, but maybe too much? Anyway, you can simply have goalline, base, nickel, dime, quarter personnel groups. You choose a personnel group, then you get the down and distance matrix. Under 1st and medium, you can then go through the plays you have in your playbook and give each a weighting. You would only see plays in that particular personnel group, so you won't have 50 plays in each choice to go through. This allows you to adjust to offenses and have a more clear goal in each game.
Simply, the way it works now really puts the defense at a disadvantage. Allowing a team to call plays through personnel choices, giving them a reasonable number of plays, and allowing weighting of individual plays really puts a better strategic element on defense. The way things are now, you can get a weird call in a specific situation. Also, the combination of LB/DB choices makes it difficult to pick a specific play for a specific situation. For example, in DB Man, LB Blitz 2, there are some blitzes that I wouldn't use in a running situation and some I wouldn't use in a passing situation. For example, OLB Blitz Inside would be terrible against a team that runs outside, but would be a good blitz against a medium or long pass. But OLB Blitz Outside would stop the outside run, but might take too long to get to the QB. So, I can use DB Man, LB Blitz 2 in running and passing situations, and sometimes get a play I don't want... but if I don't use this in those situations, the plays I want aren't available. Being able to weight individual plays allows me the opportunity to choose plays that are best for each situation. And, with this system, it is fairly easy to go in and make changes based on your opponent once you have the basic defense set up. The hardest part, here, is getting the base defense set up. You'll basically take out a few plays, put in a few plays, and make a few adjustments in various situations.