As a suggested solution:
A BFC option (tracking and range) that is 10x range, 10x size, but also reduces the tracking speed to 1/100.
That way, you can't hit anything moving in space, but gain tremandous range versus PDCs.
Highest techlevel:
range; 3.5 mkm, tracking speed at size 10: 250 km/s.
Alternatively, a special bfc that reduces accuracy not linearly, but, say, per square, so, it would have double the size, and double the normal effective range, but be way less accurate on that range, so players have a chance to shoot at that enemy, with a 0.01% hit chance^^
I guess it's honestly not really worth the effort, given bombarding planets with energy weapons is sadly rather limited.