>>3828594
Many Altmer hate the Thalmor though, so an Altmer joining the Stormcloaks isn't that improbable.

>>3828606
There is no way they could win. Of course Bethesda games can't show the true scale of the factions in the lore, but while every Thalmor you see might represent 10 in lore, every Stormcloak or Imperial soldier easily represents 500.

The Thalmor would have to take one of those 3 routes to invade Skyrim, all of those choices are suicide.