Speaking solely for the SE regional itself . . .
The top 5 boys and top 5 girls DEFINITELY would have been in the mix to qualify for the Foot Locker champs.
On the boys side, the 5 individuals (went to 7th place) would have been simply made the FL South race deeper. There probably would have been 14-18 guys at 15:05 instead of 10. Burcham would have been the only one competing for a top 2/3 spot, but the rest could have been in there.
The girls are the same way. Wesley Frazier would have easily qualified for FL as she has previously. The top ten at FL South ran 17:32 and better. The top 5 girls at NXN SE ran 17:36 and better. The course was definitely slower at NXN, so add those girls to the top 10 as well.
Basically, the SE is definitely sending 5 boys and girls to NXN who could just as easily be running Foot Locker.
All in all, I think NXN just gives more kids a chance. It's not as intimate as FL, but just as competitive. The bummer is that we no longer have the top kids racing at one race. Now both races are diluted b/c kids are splitting and choosing one over the other (in most cases).