Just saying that its a very niche fetish that could easily be expanded by simply having an option to start as a girl. It wouldn't take much writing and would open the game to a lot more people. That way he can have the best of both worlds. I mean maybe this is just a passion work for him and he doesn't really care about the revenue he put in, if so that's great for him. I'm just thinking about it from a business perspective I guess; sorry.
The plot of this story, is that the main character was transformed into a girl. He was removed from his place of power and comfort, and stuck into a body that constantly betrays him. To change that, would be to change the entire narrative. Every scene and character interaction would need to change. I'm writing a classic fish out of water story.
As for business perspective, to answer that, we'd need market data. By writing a fetish story, it helps my work stand out in a sea of other erotica. Okay, but it will also alienate people due to that fetish. Is it gain, wash, or loss? That is where I'd need market data to answer with any degree of accuracy. The counter to this argument, is that by including a different route that is selectable, I'm purely adding fans. Well, do those fans convert to patrons? At their conversion rate vs TF/TG fans or better? Unknowable from my point of view. Also, I'm just one person writing this. If I have to half my speed writing a bunch of stuff the other group doesn't care about, IE non TF/TG stuff, would my other patrons get bored and leave? Unknowable from my point of view.
I did business analysis for a few years. I can't answer clearly if going the fetish route is a positive or negative thing. A lean, market competitive project vs a circus tent project is a classic business argument that can only be solved with market research. Probably the only people that could answer that, are the people whose ads play on this site.