Changing Character Models

Lately i have been wondering the forums and an idea came to me, why not completely change a characters model such as changing lann's character model into that of the knights in Ortel castle, fiona into chuilin or evie into Ingkara. So, could you do that by finding the characters hfs file and replacing it with the monsters file? Or is it a lot more to it than something that simple?
And i head that most Hfs file mods are dont work since the patch so is it even possible to do it now?

Good Stuff Lite basically allows you to do that. For example changing DK with Succubus.