I read a paper on the topic a few years back. My recollection is that once you go faster than about 0.3c it becomes impossible to shed heat faster than you gain it from collisions with Helium. I'll try to dig it up.
The conservation of momentum means that whatever system you devise, the spaceship would have to eventually withstand the forces related to the total dP/dt required to get the obstacles out of the way...
You could change the distribution of the forces at best but I'm not sure whether that could be enough...
I read a paper on the topic a few years back. My recollection is that once you go faster than about 0.3c it becomes impossible to shed heat faster than you gain it from collisions with Helium. I'll try to dig it up.