Originally Posted by Benedict
I quite like the suggestions for online activation & login giving additional perks with a basic vanilla game playable without any additional checks.

This is how Stardock works - though of course, the additional perks in this case are patches and multiplayer support (Sins of a Solar Empire is the example I have in mind). Obviously, such a method wouldn't work for RPGs or many other genres, but if it works for RTS, then it should be used!