As of now, they're just too small and don't really have top end speed. It's like watching a league of Cole Beasley's at every single skill position and AJ Shipley's at every line position.
The German league and some of the Nordic leagues are starting to produce some players that could project to NFL offensive linemen, and they had that really good WR (Moritz Böhringer) a few years ago. I think we will see someone make the jump in the near future.
I was just at a coaching convention this weekend at USC and the Japanese league had a group of coaches trying to get some information. They were (overly) excited when Sean McVay spoke and like me, underwhelmed when Clay Helton spoke.
Besides, my point in highlighting the Japanese and German leagues is to point out that there are leagues around the world that I think make better alternatives to the AAF and other such American off-season leagues.
The mere fact they have to put it in the offseason puts them in a disadvantage straight away. Unless they start near the draft, people are tired of football. Yet, if they start near the draft, then they are about a month removed from the CFL season which, Imo, has better talent. Also, by restricting to that time, they can't expand teams because they would have to expand games. So, that's no good. So, it makes more sense to me to find already existing International Leagues that play during the NFL time to serve as pseudo-development leagues. Those leagues are not affected by the NFL like the AAF is. So, they don't lose too many fans during that time as that's when the games are played. So, perhaps teams can contract with teams there or something to that effect where they can loan a player for a season, then call then back the following year. Doing this would give these leagues NFL sort of caliber talent to help gin up further interest. Also, if the NFL teams find players like a Japanese kicker or a German safety that they want to invite to camp, then they can.