I have this idea for some time and would love some opinions about it:
It's an alternate universe type of series about "soccer" in the US. In this universe, "soccer" is the english word for Futsal. The NASL was founded in the early 60's (in real life it was 1968) as a futsal league, with similar rules as the ones we have today. The league would evolve over the years, and the sport would be as popular as today's NBA. It would be cool to test some rules concepts like, for example, a hockey style offside line.
Design-wise the uniforms would be more "american" style in the sense of wordmarks over actual badges and stuff like that. Also, courts would evolve in the same sense as basketball courts have, with use of colors and patterns (even ads on the sidelines in the more recent ones). For the teams, I would probably use some of the original NASL and MLS identities, with some tweaks of course.
If I end up doing it (I have some stuff sketched out already) I'm not even sure if it would be a "fan fiction" type of series (not really planning on simulating results and stuff like that) or just do the uniforms and teams from each era.