The restriction doesnt make Keruga wholly unplayable
That comes down to Maleficent, Monstrous Dragons Dragon Fire ability which, like the action card that shares its name, allows you to instantly banish a chosen character when you play the card
Nahiri, the Unforgiving is a cheapo walker that can loot, and grab temporary creatures and equipment out of the yard
Tangle Wire looks harmless, and the first instinct always seems to be to try and ride out the effect to net an extra card
If you go with Wizards' official rulings then you have a limit of six players per table, which is pretty reasonable
Chapter I mostly reads, Gain control of target Sol Ring. if someone has one early, and you get the little bit of value from the Ring tempting you