Ulfric is listed as an 'Uncooperative Asset' because the Thalmor broke him during his captivity, and blackmailed him afterward. I think this means he can be manipulated to the Thalmor's ends. If you are a High elf, the thalmor in the outside areas of the embassy will ignore you, and you can even do a persuasion check to make the bouncer in front of the Solar leave allowing you free entry. Subsequently, question is, can you join the Thalmor If you're a high elf?
You can find it by traveling North West of Solitude. The Thalmor Embassy is located in North Western Skyrim. Similarly, where can I find the Thalmor in Skyrim? Overview. It is not possible to join the Forsworn, but you can side with them through a quest series and one area will become non-hostile. Encounters with them will not occur under normal conditions outside of the Reach. The Forsworn are the most common type of hostile NPC encountered in the Reach. You can, of course, enforce things like the ban on Talos worship and refuse to help some people going against them, but the Thalmor don't have a proper questline. Thalmor Justiciars that carry a Justiciar Execution Order also appear after attacking and killing any wandering Thalmor agents. The bigger thing I'd worry about is that the Thalmor have a habit of winding up on everyone's bad side.
