I think in your case from what I understand, you want to release Haxe as a mode. Check this post as it is relevant: Any documentation for creating custom modes?
I do not have much experience on this, but I do encourage you to get it in github. That is, if you are going public with your project. Feel free to discuss any ideas or ask for feedback in the forum, as there are people here that have done things similar to this. The R and Pythone modes would be projects that you want to keep an eye on as they are recent additions in Processing. You could use them as your starting point.
Kf