One of the biggest issues with further adoption of Blended Wind Body aircraft is that current FAA regs require demonstration that deplaning the aircraft in an emergency is possible at full seating capacity, including crewmembers, in 90 seconds or less [1], although studies and simulations have been done that continue to evaluate this [2]

BWB with their pax on the inside, make this very challenging.

[1] s7: http://fsims.faa.gov/WDocs/8300.10%20Airworthiness%20Insp%20...

[2] https://fseg.gre.ac.uk/fire/fseg_ped2010_bwb_paper_distrib_f...