The only thing holding you back is that you need to actually connect and damage a player with the thing you put the aura on each time to secure another go-around
Meanwhile, high-synergy EDH staples for decks with Grand Arbiter include Smothering TitheSmothering Tithe, Rhystic StudyRhystic Study, Ghostly PrisonGhostly Prison, and PropagandaPropaganda
Well Rested gives a creature two +1/+1 counters and draws you a card when it gets untapped
Still, Sephiroth rewards you heavily for building around it, so perhaps the potent villain could lend itself to some sweet brews right out of the gates
While they may not be the only ones you run for color fixing, they can fill that role if youre missing more expensive fetches
They give you Monarch and then one ability in your upkeep which is enhanced if you are the Monarch