Shockwave is a great character, but he doesn't get carried far enough. I always see him as having a sort of Hannibal Lecter mentality... At rest he is detached, coldly remote, and fiendishly analytical, but when it comes time to set his plan in motion he is heartlessly ruthless and brutally aggressive.
It would be interesting if he started to become unhinged. What if his 'logic' became an obsession, and then irrational. Serial killers have a very specific (and completely demented) pattern which they believe to be logical, and I think Shockwave would be the most frightening Decepticon of all if he fell into this sort of derangement.
Shockwave occupies a very unique role because he acts according to logic where others act according to feelings of greed, revenge, or egoism. In a way he is more formidable because he is more cautious and thorough than other 'Cons, but in another way an insane villain's randomness can make them more terrifying than a sane one.
(Go watch 'Hostage' and tell me who the scarier villain is: The cool and professional mafia guys, or the sadistic 'Crow' reject.)

And by the way, I hope you guys don't think I'm some kind of Goth freak who watched 'Silence of the Lambs' too many times. Remember, a despicable villain just makes the hero look all the more noble. Although I advocate scarier bad guys, I root for Optimus Prime.