Hat mutability research

Currently, hats are immutable in the sense that their properties -- ie max supply, details, imageURI, toggle, and eligibility -- cannot by changed once the hat is created.

This has the benefit of limiting the governance / attack surface for hats, but at the cost of flexibility for DAOs. For example, a DAO may want to add mechanistic eligibility logic to an existing hat after experimenting manually with several candidate approaches. Currently, this would require creating and minting a brand new hat.

This is a research issue, with the goal of exploring the following questions:
1. What is the design space for hats mutability? On what dimensions could mutability be introduced partially or with constraints?
2. What are the risks and trade-offs of the dimensions from (1)?
3. What is a recommended approach for hats mutability?