Alright, I did all the special quests and successfully became Guild Master of the Thieves Guild, thus the bug where Brynjolf does not talk to you didn't occur for me luckily. Karliah attended the ceremony and stood around the cistern after it was completed.
After receiving my guild master armor, however, Karliah disappeared from the cistern again. I went to Nightingale Hall and nope: the place is still in its usual shoddy state and Karliah is nowhere to be found. I teleported to her and indeed, I was back in Snow Veil Sanctum. Brynjolf also went back to his "I'm too busy to talk right now" cycle.
I tried the console command setStage TGLeadership 0 and now I could talk to Brynjolf again - however this time pretty much all other TG npc's were bugged, always talking to me as if I had just been promoted and not offering any dialogue options. This remained that way even after a wait and fast-traveling to Markarth and back, so I had to revert.
Looks like there is truly no solid fix for this, even on PC

Patch 1.4 doesn't state anything about this either which kind of svcks. But luckily it already has an entry in the Unofficial Patch buglist.