Wormholes

If we take not using an ESS as the baseline....

You risk 15.8% of your pay in order to make an extra 5.2%-10.5%

Of course, its not you taking the risk, as anyone, corp mate, alliance mate, +5 blue, neutral, pirate, alt can place one weather you like it or not. I can see this being a source of conflict/anger between friendly entities.

This could be a sizable consolation prize for roaming gangs that get reported in intel and don't catch anyone, but are fast enough to get there before a defense fleet is organized. Anyone who sticks around to disburse the payout with inbound hostiles will be a sitting duck. When you have multiple ratters, 15% of all bounties can be quite a lot, even if the pool is only an hour or two old.

Ultimately the whole thing is a nerf to nullsec ratting. You have a 5% baseline nerf, plus additional incentive for roamers to disrupt ratting, the means for your bounties to get taken by a blue, and and a penalty for those that are disorganized, or choose to dock up and wait for the hostiles to leave. If you want to avoid all those things, you have to take the 5% loss with no compensation. It rewards those who are well organized or are in defensible space where roaming gangs won't go.

One per system. If it is destroyed, the unclaimed pool will carry over to the next one anchored in that system. If it is scooped (assuming only the person who dropped it can do so), the pool resets to zero.