I 100% agree with the post treating legends a true canon, and trowing out TFA and Rebels. There's just too much that I can't swallow about the new canon. (Rotosabers and helisabers being some of them, along with "disrespecing" hyperspace
)
About the blast doors, I always presumed that ImpStars had them, because they'd be just too vulnerable to fighters if they didn't, but Thrawn doesn't mention anything about bay doors on the Chimera. He tells the Chimera to rotate and "lower docking bay deflector shields", then launch tie fighter squadrons. Presumably, the Chimera was relatively standard issue, and Thrawn isn't the kind of commander that would forget or choose not to tell the bridge to open the doors, but would tell them to lower deflectors. So, that's a case for no bay doors.