As others have said, you can do imaging on OSX, but you won't usually have the choices as you do on Windows. Also, as mentioned, the main problem may be your QHY cameras - at least with something like The SkyX. Hopefully that will get fixed soon.
As the you alluded to when you said that you were OK with using Windows for processing, I'd advise to use whatever platform you want but don't let the computer get in the way of getting your work done. If you need ASCOM then that's a pretty important technology. I do run everything on Macintosh but my hardware is pretty main stream and from long established vendors.
If I really needed a PhatTek WizBang 4000 camera to make my life complete and that camera required ASCOM then I'd probably dedicate a low-end net/ultra/whatever-book to astronomy. A dedicated machine would also give you the benefit of, as best as you can anymore, freezing the system once you get it working.
Regarding a Macintosh forum - I understand. I have used Macintoshes for a long time. Long before everyone's grandmother had one. In this case though, descisions are based on larger factors. One of the goals on CN is to promote discussion by having wider and diverse audiences. If a particular forum becomes stove piped or only serves a very small audience then it tends to die but also slices away the discussion from elsewhere. For example, if there was a Macintosh forum, there would be debate as to if other UNIX based systems should be there. Then there would be a debate about tablets running iOS (as an OSX varient). What about Android discussion? In the past, CN had more system and brand/make specific forums but they started stealing traffic from each other and this led to cross posting and confusion.
Generally speaking, most of the astronomy software that runs cross-platform is, essentially, the same on both machines and even if the software is different, the issues are more alike than different between the two platforms. I wouldn't want a Windows PhD user who could answer a question for an OSX user *not* to answer the question because they were hanging out in the Windows software forum and didn't see it. We already have a bit of this with the computer forum vs the imaging fora.
Anyway, enough, sorry for the ramble. Good luck with OSX.