Document-Isolation-Policy Header via meta tag #3

How do we feel about this one? Asking from the following perspectives:

• Are there firm reasons (security/design) to forbid that?
• Is it even feasible implementation-wise? Would it make things significantly harder/more complex?

Just like CSP, features like COOP/COEP and also DIP are very useful, and web extensions should be able to make use of them too. In order to get there, we must either implement explicit support (such as CSP in manifest.json), or allow setting such headers via the meta#http-equiv tag.