[Alneyan]

Quite a few weapons can actually target fighters, such as the APB, which deals a fair amount of damage per kt per turn. (If memory serves right, it comes second of the regular weapons, after the Ripper Beam) If you planned on making such big fighters, you may want to give them the full-sized ECM and CS as well, since their fighter counterparts are only half as efficient as the ship ones. (And possibly an additional defensive bonus, since unlike "proper" ships it wouldn't get any ship training bonus)

As for your first query, the best you would get is an artillery troop (or bomber, the name will not change much), able to deal a fair amount of damage, but with a penalty of some sort. However, range and fire rate do *not* matter in ground battle, so you will need to tweak these bombers with the regular weapons. The SJ mod gives your troops a much higher damage resistance, making the artillery a powerful weapon, but not resistant at all.