I've been following this thread to see how far it will go and how easy it is to do something like this with XCN but your reply here brings the question (which I have even for XC4 though):
P.S. although you can replace template files this way, we recommend you to keep as much "default" templates as possible - some of the templates which you replace may be modified in future versions, and the changes won't get into your custom versions of the files during upgrade.
How XCN works for soemthing like this? To compare with XC4 - I always advice clients to modify existing skin and not create new skin directory - for that same reason - XC upgrade doesn't care about anything non-XC. So custom skin in non-XC directory does not get upgraded. So if there are bugs in the XC skin (not to talk about new features) simply by copying that skin to a new one will copy the bugs and they will not get fixed with an upgrade.
From your answer here I get it it is the same with XCN. To me is sounds way better to just modify existing XC skin instead of trying to create new one