I don't really understand: 'mixer in own thread' has been in BFD2 already. What is an in-house development? And what has been disabled in current release here? Do you mean it doesn't matter if I tck/switch on 'mixer in own thread' and you mean to get rid of that parameter in general?
It was never enabled in BFD2.x release builds either: it was one of those things that were always supposed to be hidden in release builds. It made it through again, doh!
The original inhouse development of this feature (in 2007) added an audio block of latency to separate the synthesis and mixing CPU loads across two cores. Our current experiments are somewhat bolder (and without the latency), but not yet ready for prime time. We'll bed down this first release, and then start getting funkier down the track.