Chaotic Archeologists gain alignment for taking historic statues and moving them off-level. Neutral Archeologists gain alignment from bringing historic statues into their quest home. (Lawful ones get nothing, because it’s right for them to leave the statues where they were.)

Differentiate the neutral alignment by making it not really about killing. Instead, neutrals get rewarded for forcing monsters to back down, surrender, and get left alone peacefully. (Sapient monsters will beg or gesture for mercy when brought down to sufficiently low HP; non-sapient monsters will produce some other message). To keep loot fairly balanced, a monster that surrenders will drop its gear.