Reduce the level of the spell of create familiar to 2, and give it a dedicated list of summonable monsters based on skill level: Unskilled creates only kittens and little dogs, Basic will pick a random non-fully-grown dog, cat or horse, Skilled will not create kittens, ponies, or little dogs but otherwise will choose any d, u, B, or f that isn’t a unicorn. Expert will choose from the Skilled list, plus any q or w. If not doing that, as a more minor change, don’t create any monster that is always hostile.