i completely agree with Schlumpfi....when you want to make singleplayer just for practice, than its completely enough what we have right now, because you can't practice very well in singleplayer, you just have to make some multiplayer matches. Otherwise it would be great to have a extraordinary singleplayer modus, but it will take to much time and money.
You can teach them basic concepts more. I encountered player with rank Major who did not know what cp is. Singleplayer now is not mirroring normal games at all, as CPU has huge advantage at begining ( but it is very weak ai ) and game is completely different from mutliplayer. You could have some scenarios with objectives like capture that cp in 4 turns. You could have pretty good scripted ai for such scenarios. In some of them CPU would use airlift on you, in some blinds... so you can see different strategies you encounter.