I'm afraid we don't have an ETA at this time; we're currently focusing on Debian and PyPi feeds for the moment, and hope to move towards Composer later.

Unfortunately i'm not familiar enough with CakePHP to advise on how to stop the service non-interactively. I would perhaps suggest to modify the batch file to not look for an exit code? BuildMaster will basically just run whatever process you ask to, so the batch file is what's waiting...

Your best bet will be using either a Delete files action, or simply just the Transfer/Synchronize files action, along with some negative/exclusionary masks. For example... * !images !cache !web.config