Nom Anor would not operate publicly, that’s suicide. Clandestine operations could sink the Empire. Remember the Ooglith Masquers? Anor and his agents could hide underneath them and be undetectable (quite literally through the force).
Not quite. Palpatine has his own intelligence agencies, from the Emperor's Hand, to Imperial Intelligence, the ISB, among others, and they have their own infiltrators everywhere in the Empire.
The Vong could corrupt Imperials through the promise of power. I assume that many Imperial officers would still be in command even 40 years into the Empire when the Yuuzhan Vong arrive. Anor could promise several young and eager captains powerful positions in exchange for secrets and loyalty. A few assassinations and entire Imperial fleets, even the domains of Grand Moffs could be under the sway of the Vong.
You do realize Nom Anor is a pleb compared to Palpatine playing the Jedi, the Republic, and the Separatists for suckers, right? You're here glazing Nom Anor as if he was the smartest individual in the SW galaxy, meanwhile the Empire is led by a guy whose 4D-chess moves took down a 25K-year-old Republic and an even older Jedi Order.
Also, if Nom starts corrupting human officers, the Sith would find out, because they have ISB and Imperial Intelligence spies seeded within Imperial ranks. The Rebels promised the same thing to admirals and moffs within the Empire, yet those turncoats were rooted out.
There is a reason why Nom Anor and the Vong had to wait until long after Palpatine was dead for sure before making any moves. They were aware of the SW galaxy for quite some time; a Neo-Crusader force bumped into a Vong scout force 4000 years before the Rise of the Empire, and the Vong even captured Vergere during the Old Republic era. Yet they waited until after Palpatine was dead and the Empire was weakened before they tried anything. They logically knew that Palpatine and his Empire would crush them easily.
Traitorous Kuati could sabotage new Star Destroyers. Corporate Sector would go with whoever promises the most profits. The Hutts double cross everyone. And at first sign of an Imperial defeat, whole portions of the galaxy will rise up in revolt.
LOL the Kuati and the Corporate Sector are the Emperor's friends. They wouldn't betray him for complete unknowns; they didn't even betray him for the Rebel Alliance who were more familiar and moral, so why would they betray him for some weirdo aliens from another galaxy? No matter what the Vong are paying, the Emperor can match their price and double it. Also, did you forget your history? The Vong utterly abused the Hutts. If anything, the way the Vong work, the Hutts would hang on to Papa Palpatine for dear life.
The Vong are a completely alien faction whose trustworthiness is questionable. Even those who have no love of the Empire would rather deal with the devil they know than the devil they don't know.
The Empire could still win against the Vong, but it wouldn’t be easy.
A weakened New Republic and a tiny fragment of the Empire decimated the Vong so badly the latter had to settle for a total surrender and exile. A full-power Empire would crush them in a fortnight. Hell, if the NR kept their eye on the ball and had a competent leader, the Vong War would've been ended in a year. They literally had to make the NR pants-on-fire retarded just so the Vong could be a legitimate threat.