I love the backstory of D'Tan trying to unite the Romulans and Remans against Sela and the Tal Shiar. With such a great story it makes no sense for us to have to choose a side at level 10 and not be able to work together as Romulans.
If we have to choose a side, fine. But let Romulans work with Romulans, despite that choice.
Actually it sounds like regardless of which faction you ally with you're position within the Romulan Republic is neutral or something meaning you are still on friendly terms with other Republic members despite faction alliances, which is why when I make my choice I'm just going to pretend the rest of the Romulan Republic made the same choice.