What would be the difference between sub families and simply putting an object into multiple families as can already be done?
The main difference is that a sub-family would inherit the variables of its parent family, whereas two separate families would have no connection to one another.
Say we have a family called Bullet that moves left and right at a set velocity and kills stuff. Then we have a sub-family called ChaserBullet that changes its velocity in order to chase someone. ChaserBullet can now access the parent family's velocity variables in order to modify them.
Why wouldn't the approach of multiple families work? Because then, ChaserBullet cannot handle the logic for its child objects. There will be duplicated logic for each child, which defeats the purpose of the ChaserBullet family. Only the children will have access to all variables.
I assumed Sub-Families existed until today (Families are treated like objects in almost every other way). I needed them and they weren't there, so I had to come up with a work-around, which did the trick although it makes the logic a little more convoluted and isn't as clean when assigning families. You basically have to make sure that anything that is ChildFamily is also ParentFamily.
Someone asked about this a little while ago and Ashley more or less said it's not happening.
Oh! I missed it when I searched. Could you point me to the thread? Thanks!