Group Home Worlds would be a great addition. Essentially, each group could set a world as their homeworld. If no one is in the homeworld, it remains inactive, but as soon as a member with their Group Home set as their homeworld logs in, an instance is created. Everyone else who also has that Group Homeworld set will automatically join the same instance upon logging in.

VRC+ users can create groups and set the group homeworld, but anyone can join a group and access its homeworld. This would allow you, your partner(s), or a group of friends to have a custom private world that you all load into together through groups.

OR if you really like a specific Club or Group, you can join their homeworld instead. It would be interesting to implement for Events as well. Where if you log in just to go to the evemt, you can set the group home as your homeworld ahead of time so you are in the correct instance as soon as you log in.