That's the idea actually. If you wanted to send a file to another user, it would have to be decrypted from the main license first. But once decrypted, it would be no different that regular file. And that is the same thing anyone with a license can do now. It's just that there would be a hurdle of one licensed machine, instead of say 5 or 10 or more.
Sure. And there are more ways to ensure copy protection if this is the case. One way is to provide a reasonable limit to shadow copies. If your original license only allows two shadow copies (which is fairly reasonable for what one user would normally want) then then it is not going to be a problem with a factory system. In fact, they could even require shadow copies to have separate registration codes before they could work.Furthermore, if you could just work on something from a functional but not "activated" copy and then just go to the "legitimate" license to print it out, then what would stop say, a poor music lab, from purchasing a single license for the main computer and then having everyone else use the "shadow" copies (to use your term) and then just print their scores from the lab computer? I just don't think that would work.
The whole problem with any system is usually not the average user defeating the software protections, but the usual people decompiling, reverse engineering, crackers and what have you.
Any protection design is really for the masses, not the people determined and capable to defeat protections.