FireLight, I'm not sure to get the difference you make between "plugin" SDK and "runtime" SDK.
The runtime is described in the manual SDK as well as its functions. You can check its reference.
Maybe you mean a SDK for the exporer (named Exporter Development Kit (EDK) in that blog article about C2's architecture in the "Future plans" part. The article is a few monthes old but the "Future plans" still stand).
As Ashley is currently adding the familly feature to C2, undergoing a lot of modifications in the inner code, releasing an EDK is not wise right now. The code is not stable/subject to changes.
He's been writing the manual, has already put a lot of work in it and yet still has a lot of writing and coding to do.
Also, it is not because he doesn't acknowledge your suggestions that he doesn't read them or put them on his todo list.
But you have also to be aware that you're not the only one suggesting things and that he also has his own plan.
He has proven to be very attentive to the community's suggestions so far, no reason for it to change.
Also changes to the SDK are delicate since they impact all the previous works already built upon it.
And at last, I'll say it again, what transpired from Ashley directly is that, for now, the focus is on the HTML5 exporter.
The rest are speculations and rumors, and should REALLY not be taken into consideration at all.
EDIT: Also — executing a local server to execute your exported project prevents the annoying message. That's how preview works. It's a local server allowing you to execute your C2 app as if it was online. It works even if you're not connected to internet, and I think this is the solution that wrapping solutions propose.
So here goes the points 1, 2 and hopefuly 3 of your argumentation.
This point has already been discussed/covered in several topics in the forum.