As for A- and B-Wings prior to Endor, I am cool with that. The a-wing especially, seems to resemble the earlier Jedi Order starfighters. Perhaps Ashoka helped design them since they at rumoured to be her squad. They could be named after her A for Ashoka. Or the A-wing is the hyperdrive equipped version of the spearhead. The squad shown does have a Pelta corvette flying them around.
I never really bought the rebellion having the resources to design new ships, I always saw them as using whatever they could acquire, whether from stealing or allies, rather than designing new things.
All the new canon does is espouse what Yoda said: "you must unlearn what you have learned."
As things are revealed, the current and older RPG fluff is being proven erroneous.
Even in Legends the Clone vWars Jedi Fighter and he A-Wings were tied together because the chief designer of the various fighters the Jedi use in the Clone Wars was an adviser on the A-Wing project. Honesty I always liked Walex Blissex so I'm not sure how I'll feel if his role in creating the A-Wings is cut in the new canon. (In Legends Walex Blissex was a very prolific ships designer having served as chief designer on the Delta-& and Eta 2 Jedi Starfighters, the Alpha-3 Nimbus V-Wing fighters, and the Victory class Star Destroyers along with the initial design of the Gladiator class and after joining the rebellion he was a design consultant on the A-Wing and the later Republic class Star Destroyers.)
Kind of sucks that Ackbar's role in designing the B-Wing is apparently being wiped too.