Nothing wrong with a twelve fret. Some people think they sound better than the square shouldered brethren. I have an N-20 that is a 12 fret, and the lack of access to the upper frets doesn't bother me. I don't get up above 11 or 12 real often anyway. Julian raised a good point... if you capo up high, then you would starting running into the heel without getting too far up.
You mentioned a shorter scale... I might be wrong, but unless that particular guitar is custom, I think the VS has a standard (for 28s) 25.4 inch scale. The body is different, but the length from nut to saddle is the same. Being it's the vintage series it will likely have a V-neck and 1 3/4 inch nut width. If you can play it before purchase, make sure you like the neck shape. I like V necks, but they are not for everyone.
As far as the slot head, it is not as convenient for me to string them. Part of that is because I don't do it that often. All said, it's not a major problem and the cool looks may well outweigh the stringing issue. Some people say it does affect the tone, but I don't have enough experience to say. In theory, lighter is better, but who knows.
In short I wouldn't disqualify a guitar because of 12 frets or slots. My big concerns would be the tone, neck width and shape. I say if you like it, go for it. It sounds like a cool guitar to me. Norman sure makes it sound good (and he does seem to capo 3 or 4 a bunch, so I guess he doesn't mind the lack of upper fret access).