Completely agree on the piers, but bear in mind that Massport - not JetBlue - was responsible for those connectors. I may be wrong, but AA, United, and Delta (particularly Delta) worked much more closely with Massport on their terminals.
Years ago I sketched out a sequence for how Massport could do this.
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Can you re-send those sketches? The links wouldn't work.
You are correct regarding the upgrades that Delta (Terminal A), American (the their side of be expansion and consolidation) and United (their portion of B expansion) in working with Massport. Given Boston is their second biggest station, I am surprised that JetBlue hasn't worked with Massport to expand/rebuild their piers. I knew Massport was the driver on the B to C connector and the low E gate work and both projects came out great.