Or five 20-man squads, which would be closer to what NeL teams really had. (Might still be large; they were pretty bare boned operations.) To get to six teams, we'd have to cut roster sizes to 17.
But that assumes that there are sufficient catchers and pitchers to support such a division. Since the FP Strat league fell apart, I've played quite a bit in a simulation game (Bill James Classic/ STATS Classic Fantasy baseball, now defunct), and I learned there that when exploring a theme team the first thing to check is if there's enough qualified catchers and pitchers to support it.
There are 36 pitchers in the NeL set. This includes five two-way players, who have cards as both pitchers and position players: Double Duty Radcliffe, who also catches; Martin Dihigo, who also plays shortstop, outfield, second, and third; Jose Mendez, third and short; Bullet Joe Rogan, outfield; and John Donaldson, center field. (I'm a bit puzzled as to why Donaldson is a two-way player but Leon Day isn't.)
Anyway, 36 pitchers, 31 of them "just" pitchers and 5 who who represent extra bench strength when not on the mound.
That's enough for four nine-man staffs, five eight-man staffs (four pitchers left over), and six six-man staffs, a thought that would probably give Ron Gardenhire nightmares and Tony LaRussa the cold sweats.
The aforementioned Classic Game required at least seven pitchers on a team; less than that gave the computer manager fits. I suspect six is a truly more realistic NeL staff.
Then there's the catching situation. There are 10 primary-position catchers, 11 counting Radcliffe. Plus there are three other position players coded to catch as a secondary position, although John Beckwith is a disaster back there. Eleven "real" catchers and three emergency guys. At two catchers a squad, we can — barely — support up to six NeL rosters.
Which is a possibility down the road, a six-team NeL league. I'd rather do something first that involves the Hall of Fame set as well.