The nods to concept material seem to be quite abundant in this new Disney era of Star Wars. J.J. Abrams seems to be leaning heavily on some McQuarrie designs for THE FORCE AWAKENS
. The AT-AT's that were in "The Lost Commanders" drew upon some of the concept artwork for the AT-AT's. Hell, the name of the Mon Cal starship builder was QUARRIE!!!
As for the B-Wing? I was glad to see some of it's origins explored here. Quarrie referred to it as the "Blade Wing", which is where that B comes from. And the concept behind the B-Wing in ROTJ was that a flight of B-Wing fighters could take on a Star Destroyer and disable it with their heavy blasters, ion cannons and proton torpedoes. There's an illustration that I've always really liked that I believe dates back to around ROTJ, and it shows B-Wings taking out an Imperial Star Destroyer.
As for the super-laser concept? It's cool to see something like that incorporated, but noting that there are complications with how it will disable the ship's hyperdrive. From a story standpoint it shows that the ship is a work in progress as it makes its way from prototype to production. As for the gunner's pod? That's something that actually dates back to Joe Johnston's conceptual design of the B-Wing, but it looks like for the purposes of this episode the concept for the gunners pod got added onto what looks very much like the ship from ROTJ. The Action Fleet Series Alpha line actually offered up what that concept B-Wing would look like:
As for the status of B-Wings in the Rebel fleet? I think that's something that the Star Wars story group is taking on. I think they're trying to respect some of the previously established EU, but they're reworking things a bit for the purposes of the show. In the new Rebels Recon
Dave Filoni said that he wanted to showcase the A-Wing and B-Wing more since he felt they didn't get showcased so much in the OT. And he as well as Pablo Hidalgo put forth that perhaps the X-Wings and Y-Wings were utilized by other Rebel units. Given what we see of the Rebel fleet in ANH, and then in TESB, and finally in ROTJ you get the sense that there are Rebel units from all over the galaxy. That methodology seems to play out somewhat logically.