> a better approach would be for everyone to try to move to what's in BoringSSL

Google don't recommend you do this.

https://boringssl.googlesource.com/boringssl/

  BoringSSL is a fork of OpenSSL that is designed to meet Google's needs.
  
  Although BoringSSL is an open source project, it is not intended for general
  use, as OpenSSL is. We don't recommend that third parties depend upon it.

> which deliberately removed most stuff, more than LibreSSL

LibreSSL has taken fixes from BoringSSL but it has the aim of maintaining API compatibility to the point where most applications using OpenSSL should "just work" for the most part. I've not tried building against BoringSSL but form reading their documentation it seems like the API is very much a moving target.