I believe that it is not possible to use the sit anywhere script with the pod controller.
However, you can assign what you move with, aka thrusters or wheels (I suggest not using wheels) to multiple Numpad Inputs.

If you don't know how to use a Numpad Input--basically, they make anything trigger when you press a key assigned to that Numpad Input. I suppose you can set one to the up arrow, one to the down arrow, one to the left arrow, and one to the right arrow... Orrrr just use the standard thrusters Garry gave us.

I have heard of a wiremod remote controller... All I know is that it links to a pod controller and... Idk what else really... :P

Also, is it not possible to spawn seats such as Airboat seats, Jeep seats, or Car seats in DarkRP?

Nope. DarkRP disables the spawning of ANY vehicle. Im asking cause I have a dupe of a vehicle, a blue scooter, thats can be driven as long as your sitting on it, and it has no chair. I can show it so one of you if it's needed.

Darn... 3:

Then I suppose you follow up with the Numpad Input method then, if you know the basics of wiring.

If not, send me a friend request. I'll hopefully teach you a little bit about wiring.