Porteus

maybe you could right mouse click on the .deb/.rpm and convert it to xzm using context menu actions?

Packageconverter is a frontend for alien. It seems to be available only in the rpm and deb binary forms.
https://code.google.com/p/foxoman/downloads/list

Alien Slackware version is at:
ftp://ykbsb2.yk.psu.edu/pub/alien/alien-extra.tgz

To use alien, you will need several other programs.
- perl version 5.004 or greater
- rpms (the Red Hat Package Manager)
- dpkg, dpkg-dev, and debhelper (version 3 or above) on http://packages.debian.org
- bzip2 (for stampede packages)

I have only bad memories of the "dark" ages before the GUI.

As fanthom suggested, use your GUI right click menu. No black magic involved. From your file manager just right click on the rpm/deb file. There should be an option there to convert to .xzm. Unless you have a particular need to convert files into deb/rpm in Porteus, I see no reason this isn't suitable enough.