Assuming you mean "because with Ruby::Box classes and modules have an extra indirection to go though." in the second paragraph, I don't understand why that would be necessary. Can't you just have completely separate boxes with their own copies of all classes etc, or does that use too much memory? (Maybe some COW scheme might work, doodling project for the holidays acquired haha)
Anyway, very cool work and I hope it keeps improving! Thanks for 4.0 byroot!