Could you add one more item level "purple tier" and make blue random world/chest rare drop or special monster rare drop items?  Make purple/blue possible end boss drop.  Possible purple world/chest  super rare  drop?   Maybe turn down blue stats and make the current blue stats purple?  Or inflate for another tier?

Make Artifact Weapons hard to get somehow.  Rare drop quest or something maybe?  From multiple playthrough?   I like the special abilities idea.

Also, can we loot the boss at the end?  When I load my save, I see loot drop but cant get it because loss of control.