I guess i could be possible to ....
...1/ ... save a Family as a Family Template (without the objects).
...2/ ... make it possible to copy/past Family's as a Template (so, without the objects) between layouts/projects.
This way you could store anything and everything that is attached to a Family (instance variables, effects, behaviours) .... And recall it later in any project/layout .. even share it with any and everyone.
All you have to do then, to have a sorta kinda reusable behaviour bank, is add the objects.
I know a empty family needs to be addressed then.