I have it on the To Do list to make the privacy and terms pages easy to override in the site settings - at the moment it's a bit fiddly to change these.

Your best current option is to create your own Privacy/Terms pages in the CMS, then create links to them in the Extra Footer HTML field in the theme options.

If you then want to also hide the standard footer links you could do this with a snippet of CSS in the Raw Header HTML field. Something like this would do it:

<style>
#footerLinks {
  display: none;
}
</style>

Good luck!

Joe