Do MKVs support multi-angle video tracks? I suppose it would be fairly easy to realize something like that in a container format like MKV... that way you could include multiple crawls and Greedo subs, at least in the MKV.
For the Blu-ray (and DVD, respectively) this is probably much more difficult, as I haven't seen a single fanmade disc that contained multi-angle. I'm only familiar with Adobe Encore for authoring discs and it STILL doesn't support multi-angle.