it seems to me that the major issue with point to point races in multiplayer would be dealing with what happens when you reach the end, a possible solution would be that your car is simply reset (like when you roll in single player) to the top of the run. ANOTHER idea that i had was inspired by touge runs and SSR7. Designing point to points as a circuit via 2 lanes of opposing traffic might be easier on the hardware than attempting to program in reseting 16 cars at nausea. Just an idea i had to make the hopeful inclusion of pro touge runs in gt5 a possibility. 
