This might not get validated for a while but here goes:
The floor seems to be grid-like, yet the parts of the machinery which intersect with the ground do not fall neatly into these grid sections. Maybe it's a design choice, but it's very obvious with the feet in the second image, and the large pipe at the front that goes into the floor seems to be sized for one of those grid spaces, yet it doesn't end up inside one.
It just drew my eye in an unconvincing way. Maybe this is what you mean by fixing the plate under the model though.
Also, it seems like some of the parts seem tacked on, as in they aren't connected to the model in a convincing way. I'm talking about the mirror / circular lever on the left hand side in the first image and perhaps the 3 coils on the side of the raised section. These sorts of extensions tend to have a larger base where they meet the main object, as you have done with the pipes.
Other than that, I can't see anything that looks wrong / odd, but I'm new to this so I could be wrong about some things. It's a good model and I look forward to seeing your progress