Diferent button class in registration form

This can be solved with override, but its better to fix it in core.
On registration form, there is button "cancel" and "submit". Both have same class btn btn-primary. Cancel button should be less obvious and diferent color, background...
So just give cancel button some other class. If looking Bootstrap 3, btn btn-default for cancel and btn btn-primary for submit.

You could also do it with CSS (using the first-child or nth-child pseudo classes), but changing this at a core code level does seem to make more sense.
At risk of adding EVEN MORE depth and complexity to the config panel, fields could be added for button classing. I've assisted other users in restyling their buttons to match their site's styles when their templates don't make use of the standard btn classes. Being able to just enter a new class designation in config would be easier for non-standard templates AND for adjusting and tweaking individual buttons to suit other user needs.