I didn't know about that! Thanks! I'd be surprised if yum didn't support something similar, but whenever I've had to build custom RPMs, it's been the old manual srpm download way. That said, on top of my to-do list is getting Spacewalk up and running, so that I can maintain my own package repository for RHEL/CentOS/Amazon Linux similar to what I do with Poudriere for FreeBSD.
Nitpick, but on Debian/Ubuntu this is a lot more simple than you make it sound: