Thanks for your Replies!
As the Pod HD Pro X should be capable of doing the needed calculations and i am a digital signal processing student, i really like the idea of line6 giving us users a possibility to add functions ;)
At the moment it looks like it is coming down to use a good (where good is meant to describe the fitting to my problem) octaver and fx loop. I tried the approach of filtering out the higher pitch tones with different filters, but the filter adjustment options are just too poor to get sufficient results. So i am missing a powerful filtering option too i guess ;)