I agree too. It’s just the better way. I’m not an PHP programmer, however from what i see in wp-includes/template-functions.php it shouldn’t take anything more, than reformatting few vars in get_month_link() and get_day_link() (and probably in few more places – i just did 10-minutes-code-scan). And, of course, some changes in regexp within RewriteRule. Or i’m just wrong 🙂