I'd vote for:
2.1 MKV as well, with BD content following,
..then the others in similar form.

Though stinky-dinkins has a point, that it's much "nicer" to have the whole package deal, I think the opposite direction of getting the raw (and arguably most important) work done - the actual movie first - is more important.

It'd be easy enough to assemble into a BD after that, and I'm sure others would be glad to handle the assembly of the "final product" when that time comes.
On that note, I'd be down for a spleen invite to help share, plus still volunteer for getting things to the aforementioned place in one of my previous posts, when the time comes. It'd be an honor to help with making sure posts there stay "clean" and understandable.

Keeping an "official" BD release until it's really done would be best I think. It'd probably also be nicer to wait for the others to get the 2.1(.1?) treatment (I'd skip to at least 2.1 depending on lossless audio for the rest, to keep the releases at same version - you already "learned" from color correction, so I think the skip is justified), and to keep the versions lined up so that when they're all ready for BD, they're "known" to be the most solid to date, but it wouldn't hurt to leave 2.0 I either I guess. Just thinking out loud.

The only part that plays into making things more complex is the audio. It'd be a little more complex to see releases with or without the lossless audio, but if we left that to when the BD is really really ready (and to those who choose to mux it on their own), it'd be a lot "cleaner" in "release" forms
1.0 MKV / AVCHD
2.0 MKV / AVCHD
2.1 MKV / AVCHD - corrected/final color correction + 'replacement audio'
2.1.1 (?) - MKV / BD with lossless audio.

Also, I'm betting lossless audio on an AVCHD would compromise the visual quality, which I doubt anyone really wants to do, so that'd be another reason to go with keeping 2.1.1 for BD *only*