Have you not followed any of the development of the WebSockets protocol and its eventual retraction? It was originally fairly simple and used the Upgrade header

Have you not followed any of the development of the WebSockets protocol and its eventual retraction? It was originally fairly simple and used the Upgrade header that was specified for exactly this sort of thing. Unfortunately, since nobody really used it before, broken implementations in proxies are widespread making it impossible to use without opening up security vulnerabilities. Sure, http-equiv could be parsed out by the webserver or a proxy and transformed into real headers, but since none of them bothered to do that, the browsers parse them. The end result to the user is largely the same (just that you're unlikely to successfully get a 304). Expecting proxies to do anything intelligent is what's "fundamentally incompatible", not http-equiv.