JDB mentioned this in the post of trading and wanted to carve it out since I love the idea.

It would be great to be able to be try different plays, player overrides, etc to see how your team does with them. Right now it's really hard to suss out whether a change that you make has the desired effect since there are so many variables.

An extension of being able to practice plays against your own team would be to allow for scrimmages against other teams. A buddy of mine IRL plays MFN as well and we rarely face each other, I'd love to be able to take shot at beating him in a "friendly" game. Or to even go more crazy...let me sim a game between my teams in different Leagues to see which is better!