It sounds like you want to tick your pawn but bot the rest of the world. You can disable tick or change the tick rate on actors, and I believe you can do this at runtime. Maybe just make a UNG button or two to control it, then make sure all your actors implement an i terface or register for a dispatcher to change their tick.
Maybe I am complicating this. I think the engine has a feature for Pausing the game and it will basically do that to all actors except those that are marked Tick When Paused or something like that.
Unreal also has Custom Time Dilation which will leave the object ticking every frame but simulate different time for it making its animations slower or faster.