Can proteins from different viruses be gathered in one virus?
If I understand your question, you're asking if you can take a protein from Virus A, and make Virus B produce that protein. The answer is yes, you certainly can do that, although depending on the proteins and viruses there may be some constraints. There are many examples of this being done, and even more examples of making a virus produce proteins from humans or other species.  

The actual process of inserting a new gene can be pretty trivial; you can pick up handy kits of viruses specifically designed to have new genes inserted into them.  If you're putting the gene into a virus of your interest, the design process can be a little trickier; you need to be sure that the inserted protein doesn't disrupt something essential for the recipient, isn't too large for its genome, and so on.

But in principle, it's pretty simple.