Even by channeling the blast, you would be limited to the velocity blast would produce.

The ramjet would be your best choice, and performance would increase in dirty space, say somewhere near a nebula. Remember that the magnetic gathering field would have to be huge, but in sci-fi this should be very workable -- um, unless you're playing at becoming the next H.G. Wells where miracles are happening now, rather than in some distant future...

With a light sail, you would be limited by inertia, which you would need to compensate for with a broader sail, and/or a more powerful light source, possibly something portable that would travel with your craft -- which might lead to greater mass for the ship and more problems with inertia. Workable, but expect a lot of math.

Dan