The problem with original X-Factor is that would be a lot of double dipping compared to the other titles listed. The X-Men event OHCs like Mutant Massacre, Fall Of The Mutants, and Inferno contain a goor portion of the early X-Facotr days. I'd say at least half of what a volume 1 omnibus would include. That being said, since all of the OHCs I just mentioned are OOP, it wouldn't be a bad thing for new collectors.