I don't know much about http, but I believe those who say that it's very hard to get the API right. Perhaps it would be best to deliver a http client library as an independent beta package for use with jdk 8+ with a final version becoming part of jdk 10? Perhaps there can be a productive collaboration here with companies for which http is bread-n-butter?
As a precedent, jsr166 historically released independent jars in this way in the jsr166* packages http://gee.cs.oswego.edu/dl/concurrency-interest/index.html
