Honestly I'd say a 7 or 8. I mean its hard enough to grasp two universes bleeding over into each other, then there's the whole making amalgams, new histories, etc. The main reason I don't try a DC or Marvel Multiverse game is because it can get too confusing too quickly. I just happen to be above average in terms of comic book history and characters and such so it's easier for me to understand. I tried explaining how most of DC's stable of characters are from purchased companies like Wildstorm, Quality, Fawcett, Charlton, Milestone, etc. and it was like I was Einstein talking to a five year old. 

Though I think the idea I had in mind for a DC/Marvel Amalgam game would cater to everyone. The idea was rips in the space/time fabric have caused heroes and villains from the two Earths to cross over with Access trying to live two separate lives and deal with each problem as it occurs. What happens when the Carnage symbiote takes control of Hawkman? Or when Namor starts a war with the surface world and Atlantis but on the other Earth? Long story short would be Access creates a handful of new Amalgams to sort out the messes on the two worlds before all hell breaks loose and both planets are destroyed. 

Marvels of Millennium City still isn't picking up as I hoped it would so my Amalgam game [I basically just wrote a synopsis for above] will more than likely fill my 2nd RP void. 

~KL~