I may have misunderstood your requirements, but why do you say that most static hosts don't allow custom headers to be set?
I know that Netlify does[0], and use it myself, so I would expect the other big names to support something as well.
I know that Netlify does[0], and use it myself, so I would expect the other big names to support something as well.
It didn't out right kill the project, It'll work under these specific conditions but reducing usability is not helpful.