I say just pick someone that can do things for you that Lucario cant. While i do post here a small bit, my true number 1 main is still Diddy Kong. But I chose Lucario as one of my other mains because he can play defensive much more efficiently than diddy, with his better projectiles, counter move, and use of spacing.
So again, think of what your lucario (not sure how you play it, offensively or defensively) cant do, and then find a character that can do those things quite well. When i think about it, Lucario cant kill at low % in air as well as others, slowish smashes, and can't counter long range projectiles. I'd say try Wolf, just because i like Wolf more than Fox/Falco.