Some prospective adds from Commander Legends:
The 4 good courts. The 2 flash 3 drops, Ocean Thief helps curb the amount of value monarchy will generate. Archon is more of just adding a tinge of monarchy to white, Sun Titan has been mediocre for a while.

A couple extra cards from ZNR:
Recovery is just a solid card, I want to try Stormcaller, it's the much better new 'Sea Gate' card, plus it can attack for monarch concerns.

General changes:
Maze of Ith has much more value now that it can protect the monarchy. I've shifted white from a straightforward aggressive deck, to be much more disruptive, and it doesn't change the clock much. Pridemage was never played, and Teeg can hose certain archetypes if unanswered. Lowered the curve on red to differentiate it from white more. Combat celebrant slots in nicely (warrior for Intimidator, human for Winota, combos with Kiki-Jiki and Twin as well, and just helps close games). The small eldrazi are back out, there's just not room for them at 540 (which means we get fan favorites Gilded Lotus and ... Smokestack? back!). Hangarback really shines in Tolarian Academy and Wildfire strategies, and I think Foundry fills a similar roll, while also just being neat. I've shifted black's durdly cards to more aggressive cards that work with Braids and Smokestack much better. Elves of deep shadow was a bad card (and the art looked super weird in Futureshifted border), so boreal druid is a clean swap with limited issues (and it's snow, if that will matter).