There's no need to build around her, Belle is universal utility to be slapped into every Sapphire deck.
Feldon of the Third Path Feldon of the Third Path is an awesome tool in artifact-heavy decks, and it can also be your commander
They are: Aeve, Progenitor Ooze Experiment Kraj Felix Five-Boots Mimeoplasm, Revered One Prime Speaker Vannifar Slogurk, the Overslime Slurrk, All-Ingesting The Mimeoplasm Umori, the Collector Vannifar, Evolved Enigma Aside from them, there are other commanders that synergize with oozes and their abilities, including: Atraxa, Praetors' Voice: Proliferate Muldrotha, the Gravetide: Reanimation Adrix and Nev, Twincasters: Token doubling Xavier Sal, Infested Captain: Proliferate and populate Morophon, the Boundless: 5-color shapeshifter commander Yidris, Maelstrom Wielder: Cascade Shalai and Hallar: +1/+1 counters Wrap Up Biogenic Ooze | Illustration by Lake Hurwitz Woof
Majestic Genesis in a Maelstrom Wanderer deck is going to be kind of silly (which I guess could be said about a number of cards)
You can even mix and match different printings so long as the total number of copies you've collected across all printings meets or exceeds the number you want to use in your deck
Then you can landfall and mill one for playing later or other good stuff too
