Board Thread:Skyrim/@comment-13842697-20140513020142/@comment-24261859-20140513021018

A Thalmor would ideally not join either side. They want the war to go on as long as possible, and the current stalemate is great for them.

If you really want to join a side, go Stormcloak but don't finish the line. I did something like what you're doing, and made it so that they wanted the Stormcloaks to gain enough ground that the Thalmor would be justified in occupying Skyrim further.