Hi Damir ,
I am not quite sure what you mean , are you saying you want to have a model in visualize link to another visualize project? kind of like how a visualize project can link to an external CAD file?
I am not sure how useful this would be as you cannot manipulate geometry in visualize , if it is appearances you are concerned about you could always try the auto-paint functionality to make sure that imported appearances always have the correct material applied to them.
unless, of course, I am totally off base and misunderstood your question
I mean just as you said.
The point is once you paint a specific item in visualize and then import that to another visualize project it would be nice to update those visual changes.
I mean that because it's faster to work on smaller parts than painting a huge assembly.
Basically now you have to either change appearances in full assembly or make a "final" version of appearance before importing to the big one.