I did an rfe recently making the observation that companion power is limitless. The toughest enemies in the game can fall to the cute puppy if you level him up enough. I think this problem needs to be brought under control before stat boosting is allowed. Even without the out-of-control leveling, I think companions are perhaps the most potentially busted part of the game and might require a deep rethink of their implementation. It feels like the game was balanced around mano-o-mano fights.
While your suggestion makes logical, intuitive sense, looking at it from the angle of 'what does this actually do for the gameplay?' I can only see it falling into the category of either 'pointless' or 'ripe for abuse'.