Thank you for the report, and interesting news about the new flight at HPN. I used to live in Westchester County and HPN was so convenient, compact terminal. I remember a small observation area upstairs of the terminal with a small bar/restaurant with a sushi bar. However, limited flights from HPN and fares out of HPN most of the time higher than JFK/LGA, my flights often ended up from LGA.
It is interesting to learn about the BDA-HPN flight. My understanding is that even with international flights with the U.S. pre-clearance at the origin airport (BDA has the U.S. pre-clearance), still the first port of entry to the U.S. (first arrival airport in the U.S.) needs to be staffed with the U.S. border protection agents (immigration/customs) and ready to meet the arriving flights when it is warranted. I did not know that HPN was staffed with the U.S. border protection agents.