Once upon a time, I was in an El Hazard PBEM, (http://www.geocities.com/Tokyo/Garden/8455/ for the curious, not that there's much there anymore).  It didn't work out too well because there was no plot,  and show characters being run as PCs.  Since then, I've moved on, and am now the Admin for several Macross based message board RPGs.  

I've been considering an El Hazard game recently, and the thought of show characters in it, even as NPCs, doesn't thrill me too much.  I suppose that's because Ifurita is so powerful that she tips the balance.  One could run a potential game in the time period before Makoto goes to retrieve her from Earth.  

I'm personally thinking about running one that takes place in a different time period altogether, probably a generation or two before the OVAs.  *shrugs* I still need to do some background research though, but I think it would be interesting, because you could play in El Hazard, without having to worry about being upstaged by the show characters, or about the GM getting the show characters right, or whatnot.