(My English is not so good, so the following paragraph is translated with a translator)
This is one of the ways to increase the difficulty of the game, and I think it has features that help me to increase the difficulty of the game. I'm glad to see that this plugin has such a good future and potential!

Interesting plugin, definitely has potential. And it's open source! Excellent.
I like the plugin so far, but I do not recommend it for "production" servers where the content is displayed to players who may also be customers. The idea of making the game hard is interesting, but doing so by embracing the idea of "bullet sponge = hard" or "less gains = hard" is not a fun way to do it.

I would recommend implementing features which require the player to use their instead of giving in to the power creep.
Maybe hooks with other plugins that add seasons or special mobs to utilize their challenge? Or perhaps class selection to to provide players perks and debuffs based on their selection? Possiblilities are limitless when you're working on making the game more difficult.

Can't guess what your ambitions are on this plugin, but you can easily implement a lot of new things if you wish to spend the time.
Nevertheless, I am interested in seeing more from this plugin.
Cheers.

The plugin is raw ... I can advise you to tweak the brains of mobs, but not how the author did here ... I am the one who does not support the increase in difficulty due to the increase in hp and damage from mobs