I can assure you that the four paths will be very different, and won't just be the same thing with a few different scenes.
For the harem part, I still think it wouldn't work in this story, with these characters.
It seems highly unlikely to me, for example, that Theresa would agree to enter a harem with Angelica, the religious symbol of purity she's sworn to protect. Or that Saki, a princess, would agree to enter a harem with several key figures from a country with very difficult relations with her own.
There are other reasons, but it's hard to talk about them without spoilers, so I'll stop here. Too bad if don't like it, but I understand, if that's not your thing, that's not your thing.
Actually that does answer one point, replaying something 4 times just for maginally different scenes and the same story is annoying as hell. So fair play, perhaps I'll give it another go after all.
Obviously don't give spoilers, however I have to disagree on the religious front being a hinderance, all religions are different and with a fantasy setting you can do whatever floats your boat.
I'm part Asian/muslim heritage although I'm not remotely religious myself and it's a curious paradox amongst the religious nuts/normal believers to think it's normal to both have multiple wives, my Grandfather had 3 at the same time, while also fucking everything else that moves... I do mean everything, and to expect all women to be virgins and never even be looked at by another man let alone talk to or god forbid... reveal thy hair to. How they imagine that works is beyond me but they genuinely believe in it, it can be totally fine for the men to rape women, they don't even think twice about it, yet all women must remain virgins for the family honour.
Belief works in many ways and personally I find the most exciting stories are when characters very thoroughly have their beliefs challenged, otherwise they never grow and character growth is story. So I'd argue that because Theresa would never go for it, is the perfect reason to write it, it makes it challenging, exciting and moving as she's then got a serious journey involving actual growth ahead of her. Her beliefs should either way be challenged as the story clearly asks for that so that's a perfect route.
As to the political relations, that's a pretty common thing to be honest, look through history and you'll find countless marriages between former enemies in order to secure alliances, those often didn't hold anyway and then you have all the drama of which side is picked or forced etc.
Don't get me wrong, I'm not saying the story should be different to the story... A writers gotta write, without being told their story isn't the right one. I'm just saying within fiction there's infinite freedom to do whatever you want, countless ways to make it make sense. I'm working on my own at the moment and there's multiple versions, one where everything goes to shit and one which is just a happy harem romp, but there's purpose to it and it does make sense even though a lot of what you've said could also be applied. There's political tensions galore, a main LI, princess of another kingdom believes her brothers murderer is the MC, can't get worse politics than that, yet in all versions, including the original which is not my writing but a very popular series I'm fanficking basically, she is very much in love with the man she believes killed her brother.
Never say it wouldn't make sense is what I'm getting at, don't want to write it like that, totally fair, but couldn't fit... nah, anything can fit anything.
