I don't think The Bloody Mute character (from how you describe it) is a character in a normal story. Hell, that might not even be a submissive, but a martyr, like Christ. I think that's a whole different concept than submission.

Nah, definitely not a martyr. He kills to protect, and does the beck and call of the patriarchs for protection purposes. A total submissive. I was interested in his backstory, but sadly the movie never explored that aspect of the character.

It didn't actually try to espouse the concept of submission, but destroy it with a girl boss ending.

Yes, and no... her being a submissive is showcased in flashbacks to her past, and a tragic event that eventually led to her not being submissive anymore, which is what then led to the ridiculous girlboss ending. However, the broader point was that the character was completely interesting before she became the girlboss; so the movie had a good hook with the audience trying to figure out what happened -- and in that regard, the writing was well done because it showed how a submissive person could do heinous things for what they believed to be love.

The girlboss revenge nonsense was just tacked on to be progressive, and while I haven't looked, I'm pretty sure most people who would be critical of the film probably also found the third act to be overdone and ridiculous.

it also really doesn't fit because submission is what would happen at the end of the story. It's what happens when the woman can finally, safely, trust her man. It's post conflict.

That actually reminds me of the ending of the film Martyrs, which does hook into that point... but not in a copacetic way. And yes, Zardoz also follows a similar concept, of the woman becoming submissive post-conflict.

But, it can also work very well for maintaining interest and being a positive character trait in dire circumstances during the conflict it self. A good example is Lane Carroll in The Crazies (the original from George Romero), who basically left all the decision making up to Will MacMillan's character, and essentially submitted to every decision he made. In this way, her character made sense and became endearing because she was doing what was required to survive, trusting her life in the hands of someone else. But it made sense, because without him, she was not going to make it (spoiler: she still didn't make it, but she wouldn't have come as far as she did without being as submissive as she was to MacMillan's character).