Thanks for all the answers.
> To my knowledge there is no way to reset character values
Shame.
> you can download level 100 characters
Thanks, an editor would be preferable, but these are still a great time-saver.
> Ascaron Frown on that kind of stuff
Yeah, that became pretty clear the minute I started googling the subject.
I don't understand what they have against cheating in single-player though. Especially since there is a god-mode cheat code available, it would be trivial to have it in internal development versions and disable it in public version. Also - with that attitude using downloaded, pre-made characters could be classified as cheating too.
In Diablo 2 there was a nice cheat/feature - ability to start new chars in act 5 / normal difficulty with 33 level char. And since there were 5 acts * 3 difficulties, and 99 levels max., that was effectively skipping first 1/3 of the game. That's a good example of "time-saving cheats".