User blog comment:Madman97/You know what really grinds my Wabbajack's? S3E5: Lack of Thalmor Involvement/@comment-24130900-20140117204305

I can think of two great reasons why having a joinable Thalmor faction in Skyrim is a terrible idea:

First, the Thalmor are intriguing precisely because we don't really know exactly what they are up to. We are free to build them up into whatever we wish them to be. Can you imagine, though, having that mystery stripped away and replaced with Bethesda's usual level of clumsy narrative? They won't be the absolute awesome machivellian manipulators you may consider them to be. Instead, you'll learn that Elf-Dave and Elf-Steve are vying for control of the local garrison and you'll realize that, while nefarious, the day-to-day work you'll end up doing is, like, sneaking into houses and tying knots into some poor Nord guy's beard or spending 20 minutes punching on a guy because your boss thinks he "smells like a Talos-dude" or something similar. They would become familiar, lose a lot of their mystique, and even come across as laughable or silly.

Second, by keeping the Thalmor vague, Bethesda has a lot more room to use them at antagonists without having to constantly trip over and account for continuity errors between games/expansions/anime-dating-sim-spinoffs. It gives them time and narrative space to develop them into something more concrete in a later installment. In Skyrim, the Thalmor are a side-show. They may have instigated the civil war, but they don't need to do much to keep it going. Other than snagging the occasional rare artifact or nudging the war along, there's not much for them to do except try to flush out Talos worship (which would be BORING without any sort of major, organized resistance to it). Trying to make them a major player in the context of Skyrim's narrative is wasteful. Better to keep them as major players for a game where the PC ends up reuinited a shattered empire.