Furthermore to that, I would construct my fighters out of pure diamond. It is extremely tough, and would also be an excellent beyond anything else to sink the energy received from energy weapons. Just like a heat sink, you can then just radiate the energy or use the energy for work, as in charging a weapon via whatever heatcycle you want..

Well the dynamics of the universe do not rule that all navigable space for combat is in vacuum that is devoid of matter. You may very well be in a nebula or even atmospherically dense gases in any number of scenarios, hell you could be flying your submarine in a gas giant, deep diving for safety.