I guess my question is related to somehow assembling and fueling a falcon 9 in LEO then launching it. I would say if all stages were fully fulled and the Merlins were all vacuum optimized.
Situation 1: How fast could it get up to with no destination in mind and you burned all the fuel.
Situation 2: Lets say its heading towards Mars and you wanted to leave enough fuel to get into mars orbit. Then how fast could you get there?