Energy weapons and capacitors?

[Havear]

Or, potentially, allowing multiple shots per sub-pulse, at the risk of overheating and exploding.

[Bremen]

What you're talking about, overgunning a fighter or similar, is interesting but in a sort of different way. You wouldn't really need a battery there, and instead I think it would be better dealt with by some extension of the reduced size laser research line.

For missile launchers, the tech line goes:

Reduced Size .75, 2x reload
Reduced Size .5, 5x reload
Reduced Size .33, 20x reload
Reduced Size .25, 100x reload
Box Launcher (.15, no internal reload)

Lasers currently only have
Reduced Size .75, 4x reload
Reduced Size .5, 20x reload

It might be interesting to add a bit more to this line, something like
Reduced Size .33, 100x reload
Chemical Pumped Laser (.25, no internal reload)

The former would let you make a sort of "once per battle" laser defense platform for, say, jump points; and the second would let you make fighters with large, single shot lasers (or a bunch of small ones, but larger is probably better given how beams do armor penetration). A 40cm laser fighter would do massive damage if it got to point blank range.

[Rabid_Cog]

I've never been able to figure out why a laser takes so much longer to reload than a missile launcher with the same size reduction.

Technically, a no internal reload design is quite possible. Just don't put a reactor on your fighter 

[Bremen]

I've never been able to figure out why a laser takes so much longer to reload than a missile launcher with the same size reduction.

Balance wise, probably because doubling the size of a laser is much larger power increase than doubling the size of a missile.

Realism wise, probably because the charging mechanism of a laser is a much smaller component than the reloading mechanism of a missile launcher, relative to their respective weapons.