Omfg - yes, calamares give root a password if you decide that calamares should do so - to make it even better, one could choose to take the same password as the first user - erm, we disabled that one, so it is not the default.
And hey - calamares is mostly python, it is well written and simple to understand. So nothing should stop you start hacking and make it better. Btw, thats what i did - found a bug, fix it and it get merged. And the calamares girls and guys are nice people.
EDIT: Damn, piper, you are to fast for me.
EDIT II: Calamares works fine with sddm - so if one set the two hooks, things becomes really comfortable.