I’d love to see more Starcraft heroes in the game. While the game is smaller in scope than the other franchises (which is quite unfortunate), the game has many more named characters than I think most people give it credit for. Just in the scope of unique zerg characters that could be cool to see in game, excluding new named unit characters like Blaze, Morales, and Probius, we would have:
And beyond those, we have dozens of the other races still available. My personal wish for diversity is getting a hybrid into the game, like a Hybrid Reaver.
Here are some examples from my personal concept collection: