Custom games are a way to bring players back.

Like forge in Halo, custom games in minecraft, roblocks, or fortnite, custom games helps players experience and express themselves with friends.

I am suggesting developing a method to introduce a suite of creative tools for players to build unique ideas in magic.

Think of Dan Dan. It's weird, best for building friends, shareable, and cannot be reproduced online yet
Once a system is useable, allow users to share these creative maps, custom rules, and deck lists.

Custom rules could include:
Shared library/graveyard
Starting setup pieces (graveyard, battlefield, emblems, hands)
Infinite mana
Life totals
Just to name a few.

This would be an asset to the brand of Arena as the place to experience magic.