User blog comment:AveryWood/Reasons Why Going With the Empire is Better/@comment-1786741-20120817053847/@comment-1786741-20120817055310

Sadly, they can't really team up without the Thalmor knowing. The Empire can't just ingnore the Stormcloaks, open Talos worshippers, without the Thalmor saying something. They did sign a treaty after all and this would essentially nullify it, leaving them open to another attack.