[Suicide Junkie]

fighter weapon that can target seekers. As far as I know, no Mod has a fighter weapon that will target seekers. With such a weapon you can have Anti-seeker fighters. At least in Tactical.

I once discussed the possibilities of such with Geo... you could have capital ships slugging it out with missiles from long range, while the defense fighters provide missile cover.
Assault fighters could be made so they can't hurt the warships directly, but by attacking the defense fighters, leave the enemy open to missile strikes.

A new mine warhead that does damage to engines or shields only. IS this doable?

not shields only, since shields do not protect against mines anyways, but shield generators only would work. Pirates & Nomads has such weapons, plus Tachyon (weapons-only) mines and null-space mines.
Very handy; capturing is so much easier when they can't fight back

Viral warheads for drones. For those really 'sick' civilizations.

Just throw a plague bomb on a drone. One less turn for planetary point defense to shoot it down, since it will fire from medium range.

New components for drones that target a planet's shipyards or resupply base. We already have such components for ships.

You should be able to toss one of those smart bomb components on a drone, and it should work.