This is an idea I had for some time, mostly inspired by modding a medium (9K) tribe on reddit but it'd be a much, much better fit for snapzu (and an admin will actually read it). This is intended as a conversation started, not a fully fleshed proposal.
This is to help smaller tribes get a good start, help discovery, and improve cross pollination.
A tribe can federate another tribe by requesting it from the other tribe and vice-versa. Breaking the relationship is unilateral though.
The federated relationship
Posting from a federated tribe appear in the parent tribe. For instance, if /t/programming federates /t/rust, /t/python, and /t/java, all of their posting could appear in /t/programming without any special effort. A tribe could be part of more than one federation, for instance /t/CanadianNews could be be in the /t/Canada and /t/WorldNews federation.
It could go many levels too. /t/python could be federated to /t/programming and itself federate /t/django.
The reason why it can't be done with multi-tribe posting
Volume knob! When you subscribe to a tribe that has federated tribes under it, you could decide how much of the content of which you want to see. Small tribes get visibility from being affiliated with bigger ones (and just from people browsing the tree) but if they post half the material of the parent tribe, they don't necessarily have to be half the content that appears. Unless a subscriber wants so. It lets you tailor exactly what you want to see in your tribes.
I also expect it would lead to the creation of lots of lounges which would belong to various community (Romanian lounge, Programmer Loung, etc.) which is where community can bond together. I found myself that posting a weekly "anything goes" topic every friday really helped bring community spirit in the community I was moderating so attaching that kind of tribe could have the same effect. And due to the volume knob, people could see lots of that or little of that, as they wish.
Once again, it's intended as a starting point for brainstorming and nothing more.