If you look at all the games through history, how many multiplayer games can you name that people have played for more than 10 years that weren't competitive and balanced? I can think of 0.
I feel like this guy's idea of a "fun" unit is one that looks cool but is strictly worse than alternatives, and losing is NOT FUN. If his "fun" unit dominated the others, everyone would build the "fun" unit and the game would NOT BE FUN.
Magic the gathering has plenty of suboptimal cards, and I do enjoy trying to "break" them. However, I only usually try to break it once or twice. Then, it effectively goes in the waste bin.
Adding a lot of cruft units to Starcraft 2 for the sake of "fun" is just going to make the game more difficult to hotkey and more intimidating to new players.
Plenty of us enjoy games that take skill to play and time to master. You don't waste that sort of time on a game that isn't balanced.