Interesting discussion here. I didn't really mind Lana had more screen time with KOTFE at least at first, because it makes sense she is the only one powerful enough to held her own against security and get you out of there. And fine Koth being the driver makes sense he knows the planet more, even if a part of me wanted Theron there. I just think Theron comes in very late on KOTFE and has a somewhat dry introduction at first. I think personally KOTET made up for it though, there was a lot more Theron moments there and I honestly don't remember much of Lana on that one besides the holocron part, which again makes sense she is the one involved with that.
I think Theron's romance arc is pretty well done at least I feel, SOR is first flirts just attracted to each other, KOTFE happens and Theron realizes how much he cares for you, and it becomes the start of an actual relationship, while KOTET we are a well established relationship and have some fun moments on Iokath and are always worried about each other. Now I can't speak on after KOTET cuz I haven't played that yet lol, but I guess the intention was to show complications that happen on a relationship, so after that is resolved, marriage needs to happen *wink, wink*. I do like Lana a lot though. I think Theron and Lana in a way are to me like the Garrus and Liara of this game at this point but I don't think Lana is as forced as Liara in this case.