A bit of a long one but I have some interesting ideas that are worth the read .
This might be a hot take but in my opinion you shouldn't be able to hot route receivers to multiple different routes. In real life this is something only elite chemistry duos can pull off, think Gronk/Brady kind of connection, even then its limited. Changing the play at the line is one thing but being able to just draw up a new play out of thin air kills the skill ceiling for playbook knowledge, both on defense and offense. There should be some sort of chemistry build up in mut between cards, this could boost their overall and allow you to do certain things like hot routes. Even then I think it should be limited to one or two hot routes per play and only four options.
For example:
You have QB Rodgers and WR Jettas, the more career stats you build with those two specific cards in mut this would influence their connection and provide a small boost when both or on the field. If they have a real life connection this would require less playing time, gain chemisty xp at an faster rate, as they know each other already irl.
This is the reason you are able to sit in two or three formations, (if that lol) and you can get away with it. This would force players to learn an entire play book to be versatile. Would make the game a lot more rewarding, refreshing and overall more enjoyable for online play. It would add skill curve that new players would have to adapt to but it would overall be worth it.
Off topic but you should be able to select your team captain in mut. This could be a player of your choice that you can upgrade through out the year and receive particular boosts. I have a Jets TT so I could pick Tyler Conklin and boost him up to team captain stats as he is a weaker link on my offense. If EA really was worried about this eating into their profits they could sell these upgrade tokens in packs at a moderate pull rate along with being able to earn some.
What do you guys think?