He's a relic from the Bush era and adds nothing to the ticket.
This. The early 2000s is not an era the contemporary GOP, or the swing voters they're trying to win over, looks back on with a lot of fondness.
I don't know what possible VP options there are from Virginia besides Youngkin; Allen and Gilmore are both dinosaurs from an earlier epoch. Tom Davis would be a fascinating one just going by electoral record, but he's been a lobbyist for too long at this point. Comstock never got enough experience, really.
Extreme long-shot option -- probably more of a Cabinet possibility than for VP, though -- would be Tony Pham. But that's only if you absolutely insist on a Virginian that's not Youngkin for some reason, and there's just no reason to do that. There are 49 more states, and several territories.