Most likely, though we could have bona fide great flyweights exclusively in the tournament? Up to you, it probably makes for more drama to have some great straws and super flies in there. Would be a hell of a fight, i can tell you that much. Plus technically Villa's a better flyweight!
I pretty much lump all of the fighters in the same general weight range. Some are naturally bigger than others, but generally they're similar in size. Even Lopez, who fought at 105, was 5'5 and had a very rangy body structure which would've made him difficult for even top notch full fledged Flyweights like Canto. Same with Gushiken and Estaba. Chang just has one of those styles that defy stylistic matchup problems. He presents pretty much the same issues to everyone he faces. IMO he was at least as good as someone like Calzaghe.
Chang was absolutely brilliant imo, to put it straight and simple. You're right about the body structures of Gushiken and Estaba, Gushiken would own that man though.
That's a pretty good list. You could put Martin Vargas up there as a peripheral, but I wouldn't replace anyone on the list for him (unless you wanted to do a tournie oriented towards guys we have film of rather than just guys that are the best per se).
Couple of more suggestions? Charlie Magri, Vic Darchinyan, Nonito Donaire, Scotty Olson, Prudencio Cardona, Freddie Castillo, Jorge Arce.
Round robin, Wilde Lynch Perez Canto easy peasy:good I think we might actually be pleasantly surprised by the level of participation,[not by me, not qualified].