It helps to bear in mind that different aspects/favors are worth more XP than others, which is not exclusively an indicator but is somewhat an indicator of the amount of benefit it brings, so rather than limit by number of things, it might be more balanced to limit it by point value. That point value can also tie into the stats aspect, with even some sort of bonus or penalty if something is useful but highly situation, or undervalued, etc

Honestly, other than the types, I would avoid the hell out of the WatP method. It was crude and thrown together mainly to flesh out stories. They retooled the mechanics and the species in the CB book, while horribly unbalanced as written are STILL better than the ones in WatP. Honestly, you're given 'Shapeshifting' as one of your Aspects in there.