At this point it's probably pretty useless for us to bump this (or the other) thread.
Still I came up with a cool solution which is not a real "solution" for our problem, but it's still a decent compromise.

http://www.speedlink.com/?p=2&cat=4131&pid=25492&paus=1

This gamepad for PC has a specific setting that allows it to work both in Xinput and in Dinput modes.
This grants it full compatibility with ALL games. Xinput for recent ones, and Dinput for very old ones like FFXI.
With a pad like this, if you set it on "Dinput" mode you'll be able to use all buttons even in FFXI.
Then set it on "Xinput" and use all buttons on FFXIV too or any other recent game.

I'm seriously considering to buy it since SE, it's pretty clear now, will never do anything to "fix" this issue of ours. (not like it would have been easy to fix it, to be honest, but still...)