In Super Smash Bros., Lucario’s most unique mechanic is that its attack power is directly proportional to the amount of damage it’s taken, attributed in-game to its aura. No such ability actually exists within the main Pokémon games (the closest analogue would be abilities such as Overgrow, etc.), let alone for Lucario, but do you think it would be beneficial for it to be implemented in the games to make Lucario more unique? Perhaps make it its Mega Evolution ability?

Hrrm.  Well, to be perfectly honest, I don’t think Lucario particularly needs all that much more in the way of uniqueness.  Aura Sphere is already a very rare and unusual thing, and makes Lucario one of only five non-legendary Pokémon in the game with a good Fighting-type special attack (no, Focus Miss does not count), and one of only two to get the same-type attack bonus for it.  He has a type combination shared only with Cobalion, and his Mega form already has an amazing ability.  From the other side, well, I don’t really know anything about Super Smash Bros., but Pokémon already has techniques that get stronger when you take damage – Reversal, Flail, Endeavour – which are fairly widely distributed.  In fact, Riolu (and by extension Lucario) actually can learn Reversal, and even gets STAB.  Those moves just don’t get used very much – by Lucario, or anyone else – because one-on-one fights in Pokémon, particularly with a relatively fragile character like Lucario, tend to be fairly quick, brutal affairs, and it’s difficult to control how low your health gets.  So… eh.  I’m not really sold on it.