(The only exception might be Garage Band with its huge sound files, but you can simply find and delete those.)
OS X is a bloated version of BSD. Why run that when you can use Linux for free? Install the software you use and nothing else. Your package manager will keep all of your software up to date for you. You won't be running an absurd antivirus program an the time...
Before anyone even starts — GIMP is not viable in enterprise workflows.
I understand completely. GIMP has never been very good (though quite usable in many cases). GTK (Gimp ToolKit) is a nice library, though. Krita is much better, but is very focused on painting.
At least you can run a real OS whenever you aren't using that specific software. Any reasonable linux distro will use <10gb including all the software you really use, and have a nice automated installer to shrink your windows/mac partition and install in the empty space.
Sure it's not ideal to have to reboot, but with solid state drives, rebooting isn't very much hassle anymore.
I feel like they could keep things the way they are, and offer an AOSP-like vanilla version for people who generally know what they're doing (Google does a pretty good job with limiting it).
I'd pay hundreds of dollars more for this software option (have previously considered hiring someone to do it in the past on a new PC, but I have had bad experiences with PC repair shops).
I bought my spouse a new PC and literally had to spend HOURS removing software and decoupling McAffee from Windows. An i5-based system was out of the box crippled while it downloaded updates and software from the Windows store that I didn't even want to begin with.
OSX is markedly better, but I don't need siri, icloud, chess, ilife, dvd player, photo booth... the list goes on.