This is a system used in a number of Latin American leagues with some success. But in those leagues, if the same team wins both halves, it is declared the winner. In the N.A.S.L., the winner of both halves will still have to play in the Soccer Bowl against the team with the second-best overall record.
This could be a disaster, as FRB pointed out in his flashback post about the 1981 baseball split season:
This created the possibility of a team having to lose to make the playoffs. Let's look at an example.
The first half in the American League East ended like this:
Yankees 34-22; Orioles 31-23; Brewers 31-25; Tigers 31-26; Red Sox 30-26; Indians 26-24; Blue Jays 16-42.
Now imagine that the second half has come down to its final game. The Yankees are tied with the Indians for the best second-half record, while the Orioles are mathematically eliminated, though only a game and a half back.
The Yankees' final game that year was against the Orioles. Now think about where that leaves the O's. If they win, the Yanks fall behind the Indians in the second-half race, and those two teams advance to the playoffs. But what if the Orioles lose? Then the Yankees win both halves, and their opponent in the playoffs is the team with the next best overall record. With a second place in the first half and a third place in the second half, that would be the Orioles!
The N.A.S.L. has to hope it doesn't run into the same situation.