Can be done with no possession and you do not even need an interface, we just need a reference to that Pawn. You’d use an interface if you wanted to control an RC car, an RC human and an RC hot air ballon. I can imagine they would have very different movement methods that could be implemented inside them.
A Player Controller can send a Move Forward interface message and each pawn class would implement the method differently.
Here’s a Level Blueprint asking a non-possessed pawn to move:
Ideally, this would be implemented in the Player Controller but you need to obtain a reference to the Pawn you want to control since it’s not possessed.