I know some retraining is allowed for familiar feats, but I'm not sure about adding an archetype. However, there is a somewhat cruel*, but effective way to accomplish what you want...
You can set your familiar free and pay the cost of acquiring a new one (200gp per character level). "Happy" the rabbit runs off to live out his days in the forest, and "Yappy" the Sage rabbit shows up a week later ready for adventure.
* What did you think I was going to suggest? There's a Union Rep for the Druids Local around somewhere...
EDIT: Or if your overall character level is still 1st level (or you've never played the character above 1st level), then you can just rebuild the Familiar for free.