I've found that wing chun and other forms of kung fu are very complimentary to aikido in both technique and philosophy. It's very good that want to augment your aikido training with something else. While many people want to suggest that you try something very similar to aikido (jujutsu, judo) I suggest you go for something from the other end of the spectrum. Not only will you develop another perspective from which you judge what you learn in aikido, you will also be able to give better attacks, in both technique and perspective, to your fellow aikidoka. One last thing, practically every martial art was developed with a philosophy that compliments that of aikido, the trick is finding someone with enough respect for the art and the qualifications to impart that aspect into their teachings. goodluck!
p.s. Aikido has no more weaknesses than any other art, it's a matter of how you train. One sensei's weakness may be anothers stongest point. Ask your sensei for answers on things you perceive as weaknesses. If sensei doesn't know, it doesn't mean that it's a weakness in Aikido, it could just be a situation that your sensei has never encountered.
[Edited by chillzATL on September 5, 2000 at 06:21am]