Instead of all AI coached teams practicing only I, Pro, and Trips on offense and 4-3, Nickel and Dime on defense, Have them Randomly practice 2 different offenses and 2 different defenses Chosen from ALL the offenses and defenses available.
That way a new coach that wants to try to use formations other than I,Pro, Trips, etc will be able to find a team that practice which ever other formations they want to play.

Or just practice all of them....

Yes, if the AI practiced all of them that would work fine.

Another HUGE idea(In my opinion) that is easily overlooked. Is to at least Double(Triple would be better) the number of Offensive Playbooks.
Other coaches I have talked to have had to limit the number of teams they have because the would like to try different Formations. But with Only 10 playbooks to customize you can use that on One Formation. Most will use 3-5 playbooks for each formation. (ex Pass, Run , Balanced, Aggresive Pass(for when behind), etc..
This REALLY limits the number of formations you can use and thus less teams a coach will have if he wants to try different formations.
I include myself in this category of coach; one who wants run different formations but doesn't have the room for all the playbooks I would need.

I agree mojo, they don't limit the amount of formations bu they do limit the amount of playbooks! This needs to be changed quickly.