Whether the work on a standard container format happens inside or outside of Docker, it would result in a format presumably a bit different from how Docker containers are now (e.g. not overlay-layered by default, since most build tooling wants to just output an atomic fileset.) And either way, work would then occur to make Docker support that standard format.
The only real difference is that, in this approach, the ecosystem also gets a second viable runtime for these standard containers out of the deal, which doesn't seem like a bad thing. You can't have a "standard" that is useful in a generic sense without at least two major players pulling it in different directions; otherwise you get something like Microsoft's OpenDocument format.
One could have just as easily said the same thing when the Docker format was introduced. The OpenVZ template format works well and is very similar to the proposed ACI format. The Docker format hasn't been without issue/problems.
However I think it makes more sense to do this on the actual Docker format which everyone already uses... That way you get the benefit of increased openness without the drawback of fragmentation. I have the impression I've been pretty vocal in asking for help in making this happen, and wish these guys had stepped in to help instead of forking. I pretty distinctly remember pitching this to them in person.
So, I'll re-iterate my request for help here: I would like to improve the separation between the Docker runtime and packaging system, and am asking for help from the community. Ping me on irc if you are interested.