I don’t have any problem with the concept; all of the Knights wear thick enough clothing that you wouldn’t be able to tell any more than you could tell Enfys Nest was a woman. My problem is that Sollony ain’t one of the Knights of Ren we see in the flashback or in any of the supporting material. She comes out of nowhere.
How do we know that? We don’t have the script.
You’re both wrong. Sollony could be any one of the knights we’ve already seen, and we do have a script (though maybe not the exact draft you’re looking for). It was leaked and confirmed as real by Trevorrow himself, remember?
Anyway, I think this article makes a very good point: it’s not the ending that messes everything up, it’s the pointlessly meandering middle. Nothing of consequence happens until the finale, which on its own is actually fairly solid IMO, if uninspired.