I've built debs by hand before. It's not hard, and it's trivial to automate with shell scripts. And once you've built a deb, you can use alien to convert to RP

I've built debs by hand before. It's not hard, and it's trivial to automate with shell scripts. And once you've built a deb, you can use alien to convert to RPM (the only gotcha is that RPM runs preinst/postinst scripts with an empty environment and dpkg doesn't). (and I say this as a diehard Arch user who came from Gentoo)