As an upside, I like this ability. It provides some interesting design space for Aura heavy formats. It'd really only work as a keyword that appears on multiple creatures, because splashing for a combat trick or pump aura would be hard to be worth it if it only had 1-2 potential targets. It would be better if the creature also had an upside for being targeted so that it was more of a build around that really paid out.As a downside, it's awkward. Your opponent always has to remember the ability exists, but it's almost never relevant because they can't build their decks with the ability in mind. I wouldn't make this symmetrical.
I agree - I don't think there's any real reason to make this symmetrical as it's almost never relevant for the opponent, as opposed Spellwild Ouphe's cost reduction which nearly always is.