[nerfman]

Gravitational forces would not have much of an effect on a ship unless it was really huge, and even then the forces would be static and not actually change during acceleration (at least if you only consider the problem in non-relativistic terms). The bottom line is that unless everybody wants to play a game where each turn represents hundreds of years and all commands are executed with a delay/lag, then some laws of physics are just going to be broken, no way around it.