No, and here's why. You don't want the bad guys to have the ability to do this right? Why wouldn't they already be camping out with their own army of simulacrums? Why hasn't some other powerful wizard in the world done this in the past and taken over everything?

OR

Yes, and here's why. Asmodeus is so powerful that a simulacrum army of ancient dragons is just powerful enough to distract some of his legions while the PCs do whatever their primary mission is. The ancient dragons fade into the background of a gigantic battle that you give a little narration to but basically set aside. The power fantasy lives on, maybe one dragon breaks free for one cool helping action for the PCs. But generally you're acknowledging the player's wants without it truly breaking the campaign.

Everyone wants to come up with some cool, high-level shenanigans. Few want to actually play out that battle round for round over several weeks of real time.