Next to the ID of the eligable crossbosses I think it is very important to also list which traits are eligable.
For example: all crossbosses where intelligence > 50 or all crossbosses that wear a hat. This way the CrossBosses start to "live" a little and they are not only numbers.
This will also help with the trading of the CrossBosses, because you have to "shop" for a specific trait if you find a pool that you want to stake in. It makes it much more fun and will turn a "jpeg" into a Boss