I have seen some topics about this and some Common NPCs do give you rewards at later ranks, but some NPCs just give you EXP, nothing else.

I have two types of ideas for an extra reward:

1. Credits Stash (based on rank)
2. Artifact (based on type)

1. Credits
At very low ranks, NPCs at their rank range gives out credits and EXP when disabling. Now, at later ranks, we only get EXP from commons. Everything gets very costly if you don't keep up with credits. Disabling common NPCs with credits will help those struggling with upkeep and upgrades.

2. Artifact
Artifacts gained from NPCs come from common NPCs from later ranks, and uncommon and rarer NPCs, but may I suggest some low ranked artifacts from commons.

Sha'din: Cloak Field Generator -> +5% cloak for 3 hours, cannot be used again if one is already operating.
Cloak = Hack, They're hackers, right?

Dark Smugglers: Mineral Stash -> Gains Minerals
Smugglers = Stolen Cargo. Why not gain a stash from its cargo when disabled? Minerals gained based on cargo space and rank.

Drannik: ???
I don't know what do give these NPCs. Any suggestions?

Any feedback?

Well, the Drannik Drones are typical to have high energy, but an energy drop would be failish.

Perhaps +5% energy max for 12 hours?