The whole problem with the partner mechanic is that it is necessary in draft, yet broken in constructed.
Yeah, that's pretty much the only reason I brought up partner. They need a way to let players build functional draft decks even if they couldn't draft a legend of the correct colors.
This solution only works in a limited environment where they can control which monocolor legends will show up.
Randomly giving partner to monocolor legends that were never supposed to have the keyword (
Urza, Lord High Artificer) is a recipe for disaster. Oh, wait-