It will be hell to customize the whole style to something different if it's based on vBulletin.
Too many elements <=> Too many features => Too many things to style from zero.
Just tell me how many pure custom vBulletin styles exist. There aren't any blank templates to start with, just a predefined default one. The only things I've been seeing happen all these years (from 2005) are color variations of the default style and maybe some image replacements. Designers/developers should have full power and the ability to do more in less time.