I support factions like volga-bulgaria and khanate of transoxiana...
More factions in the east is a good thing. In vanilla, you had only 2-3 factions battling for a huge number of rich provinces, so it became boring. Of course, a fact that it only a minimal effort was put in eastern factions didn't help. That would also make crusades more interesting, because there will be more factions in the east. Crusades in the vanilla were more of a "who will get there first". Very little challenge.
So factions like V-B or KOT will be very interesting to play.

I am really against adding burgundy, cause, as arfrisco said, it was only independent for about 1/3 of the mod, and that is the last third actually.
That means that it can not be a regular faction. Making it emerging faction would mean that they are unplayable, and would take a spot of a playable faction.
Emerging factions like mongols and timurids are a good choice because they appear as hordes. I am not sure if burgundy could be represented as such.

This game is about changing history. There is no point if after some 300 years, a scripted event like "burgundy appears" happens. Maybe after 300 years of gameplay england conquers france, or france conquers england. Or england is confined on the british isles, and hre conquers france. Since the mod starts in 1071, situation in the 1300's will be a lot different than the historical situation in europe at that time.

And finaly, gameplay. We would have to give huge armies to emerging burgundy just not to have them crushed the moment they appear on the map, right in the middle of the already established factions.

To conclude. Adding an unplayable faction, which appeared under conditions that probably wouldn't be the same in the game (ie france is destroyed), which main purpose will be to add flavour in the english-french conflict, that will be destroyed in the matter of turns if not given unhistoricaly strong armies, over a playable faction, even if it is khanate of transoxiana, wouldn't be a good decision.

And as far as Volga bulgaria goes, if Orda says they were important enough to be included, that is good for me, because I haven't seen a person who knows more about steppe factions than him...

Cheers