My second vote will be for the tribal zone of Atmora and Solstheim. I found that quite an interresting and different start.
However, they lack depth and the tribal rules sem not completely implemented.
As all the characters starts as barons (1 fief), it's really rewarding to become king and emperor, Raiding is a necessity for gold and prestige and fighting the undead at this level is quite intertaining (the attrition being often horrible).
There could be more stuff added (more lore events, more about religion, maybe a special events to destroy the frozen horde title...
eg : once the frozen horde has no more land, there could be a deseperate uprising from the undead. If defeated the title of frozen horde would be forfeit (or not)
Anything to make the war between the frozen horde and the Atmoran more thrilling and desperate...
By the way, in previous version, the frozen horde was unstopable. No it seems it gets kicked out (too often ?)...
Religion : dragon cult/priest interaction ? undead dragon event with the gain of some nice ancient artifact (dragonbone armor/weapon) and risk of being wounded / killed
I know Atmora and the Frozen Horde is WIP, but there is so much portential there
