I think a Companion Need button is a great solution. It makes life easy for everyone and you no longer need to set rules before a run. You will always have the ninjas but with a new Need option like this you will have less accidents.
Greed is already the option for companions. Once we are at 50 our companions cover all possible loot versions... So the Need for Companion is simply the new Greed and Greed is pointless. Thus Need for Companion is pointless for the start. It changes nothing worth speaking of.