No more difficult to do rail there than in downtown Dallas. Although it would have been easier with a bit of advanced planning.
Option 1: go east-west on the wide right of way of the Spring Creek corridor. (least desirable, as it would be the longest, least efficient, and least used to get people from the Legacy area to DFW and downtown Dallas.)
Option 2: 121 Corridor to the “A” Train line. Access to Dallas but not DFW.
Option 3: Follow the existing N-S rail line to the Cotton Belt. Access to DFW, but few people would take that and transfer to the light rail at the airport to go to downtown. Probably most popular for the business community.
Cotton belt is in the works, but it won’t help Legacy West.