Legions of goblin slaves to fight for them
Legions of daedric servants
Many Bosmer archers
Khajiit have sworn allegiance since the Altmer may have been responsible for Massa and Secunda disappearing
All Khajiit forces will aid them.
Can deploy the Senche-Tigers in battle (aka giant tigers that spew magic)
The most skilled war-wizards in Tamriel, able to decimate hordes of Imperial Troops
Superior weapons and armor for their soldiers
The largest Navy as Alinor is bordered entirely by sea
Not even Talos could take Alinor without the Numidium
Vs.
Man's forces
Imperial Legion (inferior soldiers)
A smaller, though adept navy
Breton Mages and Battlemages, (many in number, but usually less skilled than an Altmer)
Stormcloaks (fewer than legion troops throughout Tamriel, inferior troops)
A'klir (Redguards, the most naturally talented warrriors)
Synod, College of Winterhold, College of Whispers, Companions (Decent sized force)
Note: Can breed faster than altmer
Overall: less than what Tiber Septim had, lack of dwemer superweapon also lowers chances of winning.
Probable outcome: 87% chance of a Thalmor victory
Argonians neutral and content in Black Marsh
Cyrodils Goblins would eat the Altmer Goblins for lunch.The Altmer breed them to be tough but not too tough.Cyrodils are free range baby and tough as hell.
The dominion has no troops that are competent in set piece battles.The Khajit are not really into the whole fighting in formation idea.Plus they can be taken out of a battle by rolling a big ball of string laced with moon sugar down a hill.
The Bosmer are excellent archers but with no meatshields to keep the enemy of them they are not as effective.
And both sides could summon hordes of Dadra so to me that is a push.
so 99.99% chance Thalmor are scrod unless the Hist lickers sign on to the cause.Even then still 97% chance of being scrod

The Dracs certainly would have cause to take wing against the Thalmor, seeing that the Thalmor seek to end everything, even the cycle of kalpas. Heck, maybe you can convince the Graybeards that ending the Thalmor qualifies as "True Need".