All the Blockade NPCs have a negative effect on the planet they target, and while they give respectable rewards, what if they gave a additional positive effect to make up for the victory. These could be temporary production boosts, or maybe one off rewards.

Could have :
*T.O. HyperSeeker - As a reward for disabling this ship, the planets atmosphere is covered in a debris field, that would boost the planets defence by 15% for 2 days, as the population scavenge for useful components.

*Akulan Entity - After disabling this enemy, your scientists are able to remove the stomach of this creature, discovering samples of gases similar to the more impure Tevrazon Gas. Artefact, when used you gain a +10% boost to your ships defence for one day, immune to removal by artefacts.

*Allovore Entity - After disabling this enemy, miners on the planet are able to extract metals and minerals that aren't badly eroded by its digestive system. This could give either a temporary mineral production boost, or an artefact that grants 2 hours worth of mineral production.

As for the Kulgox and the ArcRift, i have no idea what bonus they could give, so feel free to suggest things for them

Why is one reward not enough?

sounds good +1
a kulgox drops a kulgox sac which boosts planet invasion attack by 10% for 4 hours and cant be removed. idk about the other one.

-1

as with bases, your 'reward' is getting back your lost production.