You can treat a .deb package as if it's .xz, because it is. extract it, and make the manual configuration changes. If you'd like, repackage the files into an rpm.

Back in 2006, when I switched to Ubuntu, I used to be the one complaining that developers pretended Redhat = Linux. If I had to choose, I'd pick .deb over .rpm any day.

FWIW, Gentoo offers Pinta in the portage tree:

  * media-gfx/pinta
       Available versions:  1.6-r2 **9999
       Homepage:            http://pinta-project.com
       Description:         Simple Painting for Gtk

so you could even download the source and rebuild on your own, should you need rpm's that desperately.