Sounds great! I can understand the strengths of a "focused" design philosophy like that even if I don't entirely agree. But regardless, keeping the scope not-too-crazy so you know you can achieve it reasonably is a good way to go imo.
The character gallery idea sounds good. And honestly, if the weeb-y nature of it ruffles anyone's jimmies, well, it's as you said. your game, so more power to you. everyone's a little cringy/cheesy at times, but hey, whatever makes it hotter for you in a simple browser fetish game is what works lol. And I also think it'd fit.
Hope headpats are something that is possible to be honest. Come to think of it, it probably wouldn't be impossible to also add some sort of simple tail-swaying animation specific to when you're growing them through headpats even if just a few frames, the tail is already there and just needs to be mirrored for the opposite end of the animation.
A tail swinging animation is difficult, cuz I'd want to properly animate it rather than just mirror back and forth. It wouldn't fit with the quality otherwise. Headpats I can do, though it becomes difficult when the head is no longer within patting range. Maybe I try to see if I can manage a zoomin feature...