Overall it looks pretty good, but I was surprised at how slow the webplayer ran on my old macbook pro. Are you using some kinda next-gen shaders for everything that requires DirectX 12 or something? These textures are cartoony enough that I want to say you could be using Diffuse Mobile for everything without any loss of quality, at least at this early phase of development.
Is that the main reason you're not targeting mac? Or is it something to do with the first-person movement being out of synch with the camera update in a way that just plain doesn't happen on Windows? If the latter, you should know that the product Ultimate FPS Camera on the Unity Store shows off one solution to this, (although last time I checked, that project didn't include a body you can see when you look down, so you'd need to integrate that.)
Another good option might be to add a menu where the player can turn off the first-person character's body, turn off breast physics, etc. Breast physics doesn't look right on slower computers anyway, so turning them off would be win-win for users with speed issues. That and PC users just generally like options they can turn off.
Oh, and if you actually do decide to sink money into Unity? NGUI is another project on the Unity Store that's just plain worth it for creating in-game menus that display faster and more reliably than Unity's internal OnGUI() stuff.
Good luck, and I look forward to seeing where you take this!

It's ambitious as hell.