It's entirely up to the comfort zone of the MAME development team is what I've really been getting at. They will choose to move at the pace they're comfortable with.
Honestly, you come across as somewhat badgering on this particular point. While I agree that a full build is probably a logical step forward, it's OBVIOUS to me that this is entirely outside the comfort zone of the team right now. Even more so with RB's admission that the team actually balked at picking a leader over the compilation headache.
That's more than a minor issue, that's the kind of issue that could actually *stop the MAME project cold* at this juncture.
Try checking the MAME manual at http://docs.mamedev.org