If you created on on/off switch for editing who cares how people use editing and XP. You want to play in an Online League with XP do it. You want an offline Franchise/CC with editing do it.
I don't get the whole debate about this at all. If you designed it properly you could have XP and editing on at the same time and enjoy the XP experience and then just use editing relative to attributes on players outside your team to fine tune progression to your liking. For example, if you don't want some players in the league increasing their speed because there are too many guys with 97 speed or something because of the XP progression you can dial them back. If you think all the tackles need to have 30 blocking strength because DE can't get pressure you can edit all the tackles if you want.
Just give people the option for crying out loud and they can police themselves however they want.