I think this would be a great DLC material.
I don't wanna get too much into spoilers, but As for DLC, I think this would be suitable once MQ is finished, and then you will be called by Sovngarde heroes to join their battle against Hircine. You will be able to either join Sovngarde, or decide to go on Hircine's side.
The whole idea of this would be to recruit old heroes, so you would be traveling around the Void or whatever, wherever heroes are, and ask them to join your side. Since Bethesda always finds a reason to start wars, I think they would come up with something and gave a good reason why would Daedric princes/princesses give their champions to join your cause. There could be loads of quests, many new locations even outside of Skyrim in "Heaven and Hell" however people consider it. And the great battle would echo trough eternity, while most of the people in Skyrim wouldn't even know what's going on. Basicly, I think Skyrim had enough troubles and diserves to have some time on it's own in at least one DLC.

Any thoughts on this?

That would be cool, but it looks like you'd have to complete the Companions' questline first so it wouldn't be accessible to people who don't play Warrior builds or the Companions questline.

It's true, yet many Harbingers are hiding from Hircine, and they are warrior-ish and diserve to be in Sovngarde. Kodlak or without him, I think heroes of Sovngarde would go for this, kinda seems inevitable if they hold for honor and their brothers who should be with them.

It's interesting how Hiricine gets the final say over Shor....

Would be nice as long as you could side with Lord Hircine and fend off Kodlak and his hero's as well and in doing so condemn them to serving Hircine until he see's fit to end their service

sounds good