And probably even then bringing him back probably would be easy. I trust there are still cell cultures of the Weyoun type and other Vortas / Jem'Hadar and perhaps many other Dominion species stored in biological vaults deep in Dominion territory or some such thing.
According to Memory Beta:
Weyoun 9
On orders from Odo, Weyoun was sent throughout the Dominion to search for Jem'Hadar who were not dependent on Ketracel-white. He personally identified Taran'atar as one such Jem'Hadar. (DS9 novels: The Dominion: Olympus Descending, Warpath)
Weyoun 9 told Elias Vaughn that Jake Sisko and Opaka Sulan were alive and with him in the Gamma Quadrant in 2376. (DS9 novel: Rising Son)
Weyoun remained close to Odo after the Great Link dissolved in 2376 and assisted him in running the Dominion. During this time Odo worked to change Vorta and Jem'Hadar culture for the better, but later focused on individual members of both species, such as Weyoun and Rotan'talag - hoping that both would in turn influence others around them. Due to Odo's influence Weyoun developed considerably as an individual. (ST - Typhon Pact novel: Raise the Dawn)
In 2383, Weyoun commanded Jem'Hadar Attack Vessel 971, along with Rotan'talag. In 2386, they were both among the former Dominion denizens who had taken control of that vessel and taken it through the wormhole to settle in the Alpha Quadrant. (ST - Typhon Pact novel: Raise the Dawn, DS9 novel: The Long Mirage)
In 2386, Weyoun requested political asylum in the Federation. (DS9 novel: Original Sin)
The last line seems interesting. Is he a spy or will he settle down in the Federation, maybe on station Deep Space Nine?

Anyway, no problems to bring him back. The Picard series needs something to spice it up and characters like Weyoun and Garak would be perfect for that.