If Nagant just fucking books it away from the immediate battlefield she can give insane fire support for her team due to her trickshots and her max range basically just being 'yes' (Accurately shooting Shigaraki from 200+ kms away, during a hurricane, while injured, while Shigaraki is actively moving to touch the ground.)
Course, by the time she manages that most of her team might be dead and she certainly can't fight the entire FSN servant cast at once even if she drastically outranges them by feats.
At the very least, she is a great support and could probably force EMIYA to play potshot countershot so she doesn't interrupt the rest of his team, but again thats contingent on the rest pulling their weight.