Do you think an independent Skyrim is a valid option in Tamriel with the political situation as it is now?

Yes of course it is, Skyrim has been independant before and could be again. Sure some of Skyrim her allies (High Rock & Cyrodiil) could suffer for it, and Skyrim itself would likely lose money in trade and rather essential products like food. But generally speaking the province could survive just fine without outside help. I'd expect a bit of an economic crisis however

No. The nords would be a valuable asset to the empire to fight back against the Dominion. Skyrim's independence would spell their demise when the Dominion overthrows the empire, and then attacks Skyrim in force.

It should be valid, till war start again with Thalmer who will now be much more likely to win.

I think skyrim could be independent, is now the right time for it? No honestly its not, the Thalmor and Dominion are still a threat to all of humanity and united is better.

More likely does not gaurentee victory. Hammerfell could not be conquered either. Skyrim would theoratically also only have to close down a few mountain passes to keep the enemy out for a very, very long time.

Also, if Cyrodiil would fall there is a chance that Skyrim could ally itself with other countries like High Rock, Hammerfell or even Morrowind to stand together against the dominion, an independant Skyrim would have a harder time defending against the dominion in open battles but would likely be better able to protect her own borders then they would be in the Empire.

I think an independant skyrim would provoke Cyrodiil to finally take action. Ulfric will attack the Thalmor. If they attempt to attack him first it'd have to be by boat, and they'd end up dividing forces and the legions in cyrodiil will move on in to valenwood. Not to mention Hammerfell pirates interrupting thalmor supply lines.

If Ulfric makes the first move, the thalmor again have to divert forces to deal with them, leaving the Valenwood/Cyrodiil border less secure. If the alliances are successful, Ulfric's force could be rather sizeable leaving the thalmor with a rather nasty choice. Give up Valenwood to secure your homeland, or send less troops to fight in the hopes that Ulfric's forces won't break through to summerset.