Broly, much like the other movie antagonists is poorly thought out, but his design and character are pretty cool. He's been a victim of typical Toei bullshit in the 'return' movies, though.
He isn't canon. If he were to be made canon, it could probably be done and have the highest payoff for the least retconning out of all the movie antagonists.
Knowing Toei and Toriyama though, they'd manage to hamfist it in a way nobody enjoys