I am on team 2158A, and we had the idea of using sensors and a hotkey to align the robot perfectly for picking up and placing cones. Is it legal to use AI like this to align it during driver control?
yes,
Having an autonomous function or similar is perfectly legal during driver control. If you wanted, you could be like WPI and have your entire driver control be automated if you really wished 
Yeah, but that would only be beneficial if your driver is really stupid.