I will agree that the difference between Core 3 and 4 is a little less noticeable. I'm also not quite a fan of the box additions on the Core 3 where they are currently, since in my mind, they block a lot of the view from the "windows" on the big upper disc portion of the model. The rectangular boxes would look better if they were perhaps hanging down vertically; perhaps add an additional downward "turn strut" to make the boxes semi-level with the storage tanks? That's just me, though.
Perhaps for the Core 5 model, some sort of custom self-service repair attachment could be included? Core 5s have their W&T disabled, so representing that visually would be pretty neat; perhaps give the repair attachment a miniature solar panel setup similar to the current Core 4 model.
