I am not sure if this is a bug or not. The advanced railguns are identical to the normal railguns. They have the same range, damage, power and tonnage requirements. Also the advanced lasers and carronades have the power requirement going up to match the damage they are doing. I don't know if that was intentional or the result of the underlying formula for damage?
Also how about an improved version of meson's base them off of the improved lasers range should work fine.
Brian
PS. Looking forward to 2.6