Boss System

Boss attributes will be customizable per each created. - Got it

Customization of attributes can include damage output, health, minions, and so forth. - Got that it will spawn some type of mob in the config would you like to be able to set amount of mobs that will be spawned and what their health would be also where would they spawn a radius from the boss?

^^ Yes, customizable health would be preferred, or maybe base it off how many players join the event? So it scales off a base amount. The amount doesn't need to be defined as it's just 1 per every set interval.

Any active boss will make use of it’s bossbar to display it’s information. (Health, current state) - Pretty sure default minecraft shows the wither and enderdragon info

(Indeed, but we want to show other info aswell, like the events of the boss. (Minions Spawn, Powerups, etc)


Boss Rewards

There is a base reward that all players will earn, but there is also a lucky chance of earning a higher tiered reward. (Similar to crate systems) - All online players will get the reward?
^^ Only plays who participated via /boss join, (Maybe a system to know if they leave before the event ends. (Make check via world?))

Ability to create a default rewards table, and a lucky rewards table with percent chances of obtaining. - These will be used for above correct?
Yes, the default table will be used for all base/standard rewards. (Lucky table will obviously be at random)