The A321LR/XLR actually solves a number of problems with AA's TATL operation at JFK. After the merger, AA was never going to keep/build a large connecting hub at JFK for TATL traffic. PHL is cheaper, less congested, and aside from leakage to EWR on the NJ side, they dominate the market. Going to all 777 at JFK was about two things: the horrible reliability of the 767 and the need for a better hard product. But the 777 is way too much capacity for most TATL routes out of JFK without a connecting hub, especially where there's competition (even Delta, who has a large connecting hub at JFK, uses the 767 on many TATL routes). Hence the end of most non-LHR routes out of JFK.

If AA actually outfits the A321LR with high-end all aisle seats similar to the A321T in F, it will be very competitive and allow them to go into business markets and skim the highest-dollar O/D business travel demand without having to compete on price with Norwegian at the low end. Business travelers are not going to book away from this just because it's a narrowbody. I remember when the A321T replaced the 762 on JFK-LAX and there were a lot of upset FTers, but in the end people liked it because the new planes were much more reliable and the smaller size actually gives quite a good sense of privacy. Not to mention very fast boarding/deplaning time.