This was mostly meant as a nebulous "some time in the future suggestion" when I mentioned it on Discord, but people seemed to like it, so here it is.
I'd like for there to be some crossover in beam weapons tech. Basically some techs would be shared between "schools" of weapons, so that having two types of beam weapons wouldn't require twice as much research.
For example, instead of Laser Focal Size, Meson Focal Size, and Microwave Focal Size, there could be one tech, "Focusing Lens Diameter" or maybe "Energy Weapon Focal Size" with the same cost to research. There would still be Laser Wavelength, Meson Focusing, etc lines, so it's not that one tech would give you all three weapons, but rather you'd need the focusing lens diameter + one weapon specific tech. Using just lasers would still be two techs, but Lasers + Mesons would be three techs instead of four, and all three would be four techs instead of six. Meanwhile Railgun and Gauss Projectile velocity could be combined into one "Projectile Launch Velocity" tech (maybe alongside either plasma or a third new weapon), but you'd still need to research Railgun size and Gauss rate of fire separately.
The goal here is to make it more practical to use multiple types of beam weapon, and also clean up the research trees a little bit.