Ubuntu – way to build rpm’s and deb’s on the same system

I highly recommend you look into the openSUSE Build Service. They've got all the various distros and architectures set up in Xen virtual servers, and they support a wide variety of packages, including RPM and DEB formats. It will save you loads of time and hassle setting up every one of those servers yourself, much less the time it'd take to get all of the includes and build-depends right.

http://en.opensuse.org/Build_Service

Edit: As a side note, if you have security concerns, you can download the code and set up an OBS on one of your own servers instead of using the public ones.

You really, really want to create an RPM. You shouldn't have to do it from scratch; there'll be any number of existing packages out there you can use (or at least use as a base) -- including the existing RPM package.

Installing from source in a package-managed environment is just asking for trouble, from anyone who has to administer the server in the future or even just you when in 3 years you forget what horror you've wrought.