That's where I disagree. IMO a familiar is a druidy thing, going back through the history of medieval europe and how the idea of familiars started in the first place, with christianity and satan. Obviously this is all fantasy, but I've always felt they really belong to druids, not wizards.
I think rangers should have animal companions (watch the Beastmaster movie) and druids should have familiars. Wizards could make pacts with demons for powers, giving them an imp or quasit, or they could create a minion, such as the homonculous. I know wizards have had familiars in D&D for decades, which has in turn greatly influenced countless other fantasy books and games, but the origin of the idea of familiars has always been clearly druid to me, both historically and game-wise. But it's just an opinion. : )
Here's the wiki list of familiars from BG2:
Lawful Good: Pseudo Dragon
Neutral Good: Pseudo Dragon
Chaotic Good: Fairy Dragon
Lawful Neutral: Ferret
True Neutral: Rabbit
Chaotic Neutral: Cat
Lawful Evil: Imp
Neutral Evil: Dust Mephit
Chaotic Evil: Quasit
Allowing one step from TN gives the green options for druids, all of which seem perfectly fine to me. I would say the fairy dragon is particularly druidy, even though it's not in the five options. I understand imps and quasits may not seem druidy to others, but ALL familiars seem non-wizardy to me, so... lesser of two evils.
My vorpal rabbit just critted the belt ogre for 4 damage, killing him ("lookit tha bones!!!"). Though he only causes 1-2 damage, he seems to have a high AC, great thaco, and the ability to spawn many of them is definitely OP.
Of course, right after killing the ogre, Xzar summoned another to deal with some wolves and caused a wild surge:explosion. So, I'm starting a new game. I don't like OP stuff so I'll give him something else (though I really think the bunny suits him best).
My suggestion for the rabbits is to eliminate their damage and thaco. Their role should be damage soakers, not damagers. Give them poor AC and 1 hp, and limit their summoning cap. Either one, or maybe one per 2-3 levels.