Well, one thing I'd like to discuss is ESO's newest addition to the lore and how it could affect a game set in Hammerfell. Namely, the Thieves Guild DLC, Hew's Bane and Abah's Landing. A lot of new lore has been put in Abah's Landing, and it seems to be a major city of Hammerfell, so, I doubt it could be just written off as no longer existing as of the events of TESVI. From the city's origins and its founder, to the origin of the name Hew's Bane, it seems very thought out. I think one could argue that Abah's Landing was renamed to Gilane at some point, though, with characters like Doctor Nabeth al-Gilane, Gilane could also be retconned into being the name of a region. Like Hew's Bane is located in southern Khefrem, Gilane could be located in northern Khefrem and be home to Oulnim Gate and the Khefrem Academy of Yokudan Heritage.
Secondly, new information points to the Celestials from Craglorn, at least at some point, being considered to be the obscure deities from Daggerfall. http://static1.squarespace.com/static/554f9eb0e4b051fccebe7fcb/555022cbe4b01d087a8db4cf/5552dbc9e4b051de24bd19ef/1431556236083/char_6.jpg?format=1000w and http://static1.squarespace.com/static/554f9eb0e4b051fccebe7fcb/555022cbe4b01d087a8db4cf/5552dbcae4b01424fe40d501/1431556242948/char_7.jpg?format=2500w, according to this early concept art. This has many implications for these obscure deities, and would explain why Ebonarm was removed from "From the Memory Stone of Makela Leki". The idea was clearly rejected, at least to a degree, prompting for a somewhat less interesting questline. But the correlation seems so obvious now. Hel Ra Citadel is where the Warrior is faced. The name "Hel Ra" translates to "Communion" and "Great" or "Warrior" as in "Great Wave" or "Warrior Wave". But the name takes on a whole other meaning when we consider that the Warrior was once planned to be Ebonarm, Hel Ra being the Citadel of Ebonarm.
Sai, the God of Luck, could be the Thief. That way, the Celestials of ancient Nedic tradition could be explained as being adopted by the Redguards, now the obscure deities of Ebonarm, Ius and Sai, with the Serpent remaining as Sep, the Oldest Ghost. Also, how about a conspiracy in which the Forebear merchant lords of Taneth are financing the Nordic reavers of the Bend'r-Mahk to conquer Dragonstar and their chief rival of Elinhir? Could be very interesting, especially for the Kogo-Hi of Elinhir. While the Forebears are more accepting of mages, the Crowns are far less accepting of the Nudri-Hi, or "foreign magic" and Elinhir has had a bad history with renegade mages guilds. While they may have an understanding with the High Prophet of Elinhir, similar to that of the Blackcasters, the Nords are far more accepting of the "Clever Craft".