Having used an eccentric hub from the abovementioned company (of course, it's not a cassette hub), and having disassembled it to correct a bug introduced during fabrication, I have to say that it's a bad idea. The ENO hubs are shiny but badly fabricated (high tolerances) with cheap and crappy bearings. Hugely overpriced.
It would be much better if you would just change the dropouts to horizontal or track, if you are so attached to that frame.