There is also this great "training" mode, which has 3 different stages. This kind of reminds me of Red Alert 2, which has different battle modes, where there are maps that only allow ships, or like don't allow ships. Although I forgot which was the exact term was used back then, I hope you get the idea.
So I'm thinking for custom games, maybe under settings, we could add another mode selection where you could choose: Full war, Ground only, Air only, Basic ground only, etc.. Or even have this available for un-ranked match?
Talking about un-ranked match, I see it as a great way to have fun where you could practice crazy builds with real human players, or just play without having to stress about ladder points. So why not add more options to make the un-ranked matches more fun? Yes, we could use the custom game for everything, but people rarely use that, and you'll need to talk to them to set up the ground rules if you want to play something like basic ground units only. It's almost impossible to play a game like that unless you are playing with friends.
Basically the idea is, when you search for un-ranked games, you can choose Available Troops level, and you'll be matched with other people who's searching for the same type. (Or you can choose "ANY" for faster search time). And, talking about search filters, why not add in another filter that you could choose the opponents skill level, according to their ladder rank? Maybe just a few simple options like: Even, Slightly Imbalanced, Greatly Imbalanced.
I apologize for the randomness of thoughts and bad format organizing. And again I'd like to thank blizzard for their hard work putting into this epic game for everyone to enjoy. I think HotS will live up it's name for being a big step up compared to WoL.