I can confirm that std::experimental::filesystem is no longer available after the 16.3.1 update, so if you want to use v142 then we’re forced to switch to C++17. Not a bad thing I suppose, it was going to happen anyway.
I updated my branch / PR with to build with latest, C++17 enabled, so far so good. I didn’t update boost, the only thing I saw that required it was the legacy ci::JsonTree class, which we’ve decided to remove for the release after next (see post here), so I just went ahead and removed it from the vc2019 project file and everything else built fine. As far as I can tell, we have no more boost dependencies on Windows, which is a long term goal that we’re finally reaching.