Off the top of my head, the three items that stand out as needing attention are the following:
1, Domes are incorrect, should be Budd type (rounded) vs, P-S (which the Bluebird did add later, but only one). Actually, maybe by mistake, the dome is a pretty good version of the P-S add on.
2, The observation car roof end is not correct. The end light should be raised and not recessed and the roof panels were very visible, not smooth like in the model.
3, Ride height seems even higher than other passenger cars, might be due to color scheme.
There are a few other items that should have been corrected, but those are minor.
1, The Blue window band is a little thin around the windows.
2, The Blue window band should have been continued all the way around the back of the observation car and the top blue band should have stopped right where the “boat tail” starts.
I think this leaves room for Golden Gate Depot to run a version of the Bluebird for the faithful. However... In my opinion nobody has really done, including the recent Atlas, a decent version of the Budd dome. Meaning the contours and the framing thickness, in a RTR model. If GGD cannot get this feature correct then I would not even bother making the set.
Since this piece (the dome) is removable, there might be a slight chance that Lionel could tool up a nice Budd dome and sell as an after-market part where we could make the switch on our own if we wanted. A quick message to Ryan (or Mike) might be a good starting point.
Based only on the pictures posted, the Blue Color does look to be about correct as are most of the windows.
Also, correct are the car names/numbers and the various shapes/sizes of fluting used on the roof, sides and skirts. To me, that is a very nice feature that has seemed to have been lost of many RTR models.
As with anything in O, nothing is perfect. But there is room for improvement for sure.