each character should only be able to pick one religion, and that religion depends on the one you pick on the characters creation at the start, this will encourage more people to team up so they can benefit from each others religions they chose,
this will enable more perks to be added to religions as you can no longer create all of them by yourself just the one you chose at the start.
you should only be able to build 1 alter at a time per player as well, if you want to relocate the altar you will need to demolish the previous one.
They already stated several times that player choice is number 1 priority. So you’re trying to take away player choice.
Make yourself a mod that does what you want, super easy barely an inconvenience.
Also think about the single players. You can’t play single player alone the way you want the game to be.
I can beat the game without any religion or thrall or pet or maproom. Hell I can get a legendary weapon in under an hour. I do get that someone shouldn’t be able to worship both “Set” and “Mitra” at the same time. That is like being a mass murdering pacifist. If you want more realistic game play consider joining a RP server. They players limit themselves without needing to be forced. And it’s fun.