Anyone who runs a community, especially dance/rave community, knows how much of a problem Very Poor avatars are. Also anyone who uses a Very Poor avatar knows how annoying it is being told to change avatars.
VRChat implementing features such as performance blocking has been a double edged sword. It is much easier to hide very poor avatars than it was before, but this has shifted the burden of responsibility not towards avatar creators, but towards users.
Put the power in the hands of the World Instance Master/Owner/Creator.
World Instance Creators should be able to set custom limits for avatars permitted in the world. When a user goes to join said world, the game checks their current avatar performance rank, checks the permissions to the world, and performs one of two actions.
1.) Avatar Performance Criteria are met and the user is put into the instance
2.) Avatar Performance Criteria are not met and the user is presented with a menu that has three options.
The options are as follows:
1.) 'Suggested Good Avatars' (show a list)
2.) 'Join in fallback avatar'
3.) 'Cancel'
For a minimum viable product, a preset for "No limiting" and "Poor or better" would be a great start, with eventually allowing creators to set custom criteria such as "I only want to allow [X]MB of VRAM usage per individual" or "[X] number of polygons per individual". In the UI it could appear similarly to our shield menu.