Who's going to say what is to be reset in a "full new install" and what is kept? I don't think the line is as clear as you think.
For example, the disk space. Maybe one partition was made to be a flat amount, and another gets what's left, maybe it's a percentage split. Who's to say?
What if the rest of the hardware is significantly different? Maybe your old amd setup needed no third party drivers, but your new nvidia setup is broken without the third party drivers?
I don't think copying the username / password is a good idea either, ever, by the way.
I think the gray area between cloning and just doing a fresh install without copying anything is a little too personal (and/or hardware-specific) to really manage well this way.