Good in theory, but AFAIK the retroarch devs have no intention of implementing said feature in the short to medium timeframe. lr-fbalpha having it would be a lifesaver, there are a lot of 2, 3 and 4 buttons per player arcade cabinets out there that badly need it. What's the last lr-fbalpha version that fully supports it?
Please do not post a support request without first reading and following the advice in https://retropie.org.uk/forum/topic/3/read-this-first