The bonus can be just about anything. For a legion-wide benefit, we considered that Exotica could spawn a unique boss to battle every x days. Keep your ideas coming.

Such as a return of its original inhabitants?

Honestly I would think a planet as wanted as Exotica would be equally as hard to keep as it is to steal. What I mean is make the planet undefendable, only guardable with ships then once a legion steals it then its up to the legion ships to defend it. It would be a constant battle over the planet who ever is able to keep it have it have stacking "good bonus" for each day/wk its kept. Honestly I yet to do mission cause when I started it seemed planet location isnt worth the effort and energy to finish the mission to get it if you cant take it. I dont need another planet in data base I cant use. Lol. I like idea of giving it a stackable debuff but like someone said if they abandoned and recolonized it fast would debuff be gone? Thus letting one owner keep it longer? The debuff just to me still makes planet unwanted cause then if I get it its for limited time only. Id say planet like that just waiting on debuffs to time out after few days, dont keep it in spot like like it should be. Just my thoughts, till the debuff is in action i cant say much about it.

Lots of really cool ideas in this thread. I was thinking something a little different (and/or in addition to) the above...

Since Exotica is in fact a "planet", one which NEVER has productive structures on it (ntm mediocre production stats), why not also give it PASSIVE Production...? Something VERY significant to the owner...along with the idea of spawning an NPC for the legion (maybe trigger a "spawn" ability for the owner). That would be really cool IMO, and provide all benefits and control of - to the owner.

perhapes there would be different types of exotica which you can only take depending on your legion average strength so that the little legions can have some fun.