If I may suggest something, and I think it has been suggested before, it would be to be able to do something similar to custom behaviours using events, it is not a nessecary thing, but being able to define your ennemies with behaviours that you do in events could be a nice addition for some people.
ArcadEd I think an exporter developement kit was in the todo list in the early C2, but it was abandonned, not sure of the reason. I also think scirra should not advertise third party wrappers, C2 does html5 and it does it in a great way, they cannot guarantee those exporter can do the job correctly (node webkit compatibility, cocoonjs tendency to break things + lack of memory management with C2, etc..), third party exporter should stay third party, and so be a potential option, like an added value, rather than a selling point. Since this is the current problem: a great html5 engine is mostly used outside it's bounds because people think the html5 is the added value, while it is the product. Just my 2 cents.