My two cents on your list…
- Windows Phone 8.1 has been discontinued as support from Microsoft
- Windows XP has been killed from Microsoft five years ago, enough?
- Firefox 31.3 ESR is obsolete, current ESR is 56.2. Firefox 47 is far more than superseeded, 67 is currently out.
- I am personally concerned from Android 6 error about handshaking, but i think that Chrome or Firefox could connect flawlessly… for web services. And email clients.
I think that closing doors to issues (vulnerabilities of cypher protocols) is far more important of the sensation of being protected (used faulty cypher protocols).
Providing an optional TLS policy PCI (willingly compliant) seems a great idea for me. If this will be available as optional (with a list of known-supported OSes) list should be great for help people test and feed with direct tests this list.