May be expanding homebrew.se into brewing.se would be helpful. I use StackOverflow for both my home and professional coding projects, and I would love to use (brewing)homebrew.se in a similar way but I hold back on professional brewing questions, as they seem very much off topic for a homebrew channel. For these, I use professional brewing forums on facebook, private forums and reaching out to friends in the industry privately.
Regarding beer.se vs alcohol.se vs brewing.se I could see these working well together, as a moderator I see lots of questions on this site that are about enjoyment of the homebrewed product, that people label as off-topic, but I see as a continuation of homebrewing - from grain/grape to glass.
We see questions about homebrewing, distillation, setting up a brewery, to leagl queries on selling alcohol in the US/Aus/UK to finding hop varieties native to Northern India, the remit of homebrew.se is percievied as far wider that it was initially envisaged.
I think merging beer and home brewing could work, but what about homebrewed wine?
I think merging homebrew and beer into alcohol would make more sense, and given their new definition of basically all things alcohol may make my next paragraph redundant.
To my mind what would make the most sense is dropping the 'home' section and turning it into brewing.stackexchange and attract everyone from timid first time home brewer asking "if this looks right" to 40 years experience head brewers asking for a recommendation on brewhouse designs and/or malt suppliers in the MidWestUS or Outer Mongolia.