Add in one more vote for a female MC please. I happen to be a dominant straight gentleman, but I enjoy playing player-submissive games with a female main character. Luckily for me, the current main character is androgynous enough that I can pretend he's female, but the few pictures that show his cock, or the text descriptions that describe him as male spoil it for me a bit.
If it's not too difficult to implement, I'm willing to bet that you'll attract a lot more people to your game by adding in a female player-character. It'll probably be a lot of work, but it might not be as bad as you think. A lot of your art also happens to not include the main character's penis, so you might not need to redo much art, or rewrite much dialog. You'd need to rewrite some scenes, change some of the sex descriptions, and draw a handful of new art assets. Things like receiving blow jobs could easily be changed to getting eaten out without actually changing any of the underlying sex mechanics or logic going on in the background, it would simply be a matter of changing the description strings.
Also, you probably wouldn't need to include too many vaginal variations in sex scenes. Anal sex is still appealing to many hetero people (myself included).