Right now it's cool and kind of puzzly to work out optimal bookshelf arrangements, but what if pack makers could add more kinds of bookshelfs with different stats/limits, such as a shelf that reduces all three stats, or increases Eterna but reduces Arcana.

And make it so if another mod adds something to boost bookshelf levels, then a pack maker can adjust those stats too, such a makimg it so the botania Natura pylon has a max Eterna level of 30 instead of 15.

Default configuration would leave the bookshelves as they are, of course.

They can, as all bookshelf stats are datapack loaded to begin with.