Sorry about the misleading title, this won't be a howto post as that is covered adequately elsewhere. After several hours of stuffing around and leaving the process go over night I've managed to build a working, booting version of Android for my Galaxy Nexus built on an Ubuntu 12.04 VM.
Without considering the consequences, I blew away the data on my phone and installed it - right before I had to go. Despite doing all the binary blob things, adjusting Makefiles, etc I still walked outside and didn't have a GPS. Back to stock I go.
But I do have a good idea - if I track the version of stock that's currently on my phone, I should be able to modify the parts I want, and override just the files that need to be overridden in order to achieve what I'm trying to do (specifically, I want to steal the CM/AOKP/MIUI toggles in the notification drop-down and put it on my stock Android). It'll mean when a new OTA update comes out I'll have to revert those files back, but it should mean substantially less data loss from mucking around with new ROMs trying to find one I like.
I think, anyway.