If your companion is functionally invulnerable, and the 'points' systems that govern their disposition toward you are very simplistic and easily gamed... yeah this would be very, very cheesy and janky, and because there's no real agency on the part of your spouse, along with no real risk of them ever being seriously, permanently hurt or killed, it would all feel fake and stupid.

...

But!

You could make a very compelling game with a while bunch of branching plot paths based on key, pivotal decision/priority moments relating to how you and your spouse agree or disagree on things.

Something like this, done well, could be a very compelling New Game +, for FO4, or just a whole different game.

If you made a game where... you know, your spouse can fucking die, and the game can move on after that?

No invulnerability, no 'severed thread of prophecy' shit...

If you could actually take the concept seriously, I can see a game working around the core concept of 'you and your spouse try to survive the apocalypse'.

Maybe theres certain 'good' endings where you two fight a bit, but ultimately reconcile and defeat some greater foe, achieve some good goal.

'Bad' endings where you piss off your spouse so much that they actually leave you, form a faction against you, force you into a moral bind where you have to kill them to do what you think is right.

Maybe theres middling endings where you do achieve big goal, but at the cost of your relationship, or your spouses life.

...

There are ways something like this could work, but I have 0 confidence that Bethesda is competent to either write compelling plot and dialogue for this, nor do I think they could actually code, actually structure a game that allows for all this.

They can handle basically side quests that modify the totality of an end state in fairly superficial ways, but I don't think they can even concept design a game where the actual core plot is quite variable.