Magic's best stun counter commander, Hylda of the Icy Crown offers you insane benefits for tapping creatures out just by paying extra mana
We can see him going very nicely with all those Raid Bombardments and Impact Tremors that were printed in the Wilds of Eldraine Enchanted Tales bonus sheet
On top of that, it also gives all of your Creatures +1/+1
Maybe Im Not Quite Done With This Deck After All There will always be tweaks to make, of course: Spellslinger decks tend to get swamped by big stompy creatures if the draw doesnt go your way, but after somehow packing a Confetti Foil version of Omniscience, if I can ride out potential awkward mid-games, I can start playing cards without their mana cost
It also heals your previous Active Pokemon, so that could be used as a method to power up Power Creation if you can't use Rainbow Force for some reason or another
I think even a single target Replenish would put serious constraints on the format and the types of designs WotC could safely make