The activated ability requires more creatures for a higher chance of hitting a creature
ProxyMTG uses a cardstock that is intentionally game-oriented
You can choose not to have Omni-Changeling enter as a copy of another creature
Fetchlands and fetchable duals, particularly Triomes, enable players to play three or more colors, whereas shocklands, fastlands, painlands, and any land that enters the battlefield tapped while only tapping for two different colors will push players to draft more two- to three-color decks
By the way, similar cards already existed with Truce and Temporary Truce, which got a lot of multiplayer play during their heyday - although there you could trade cards drawn for life gain if you were about to die and needed to come back
Theyre perfectly fine and probably very fun to play out of the box against one another, but they dont stand out amongst the best precons of all time