I would recommend reducing the challenge rating of the encounters so they wouldn't need so many NPCs. Otherwise you'll just be fighting yourself for 1/2 a combat.
Hey Erik.
Question: What do you mean by "run a pregen"? Do you mean "a gm can run a pregenerated NPC if the party..." or do you mean "I know a GM can run a pregenerated adventure as an NPC if the party...."
If your PCs need a little extra help, let them hire a a mercenary, or a holy man, or maybe even a cut-purse, but I would suggest against any DM run party memebers, players dont usually like them