Aside from the fact that an SMP server would not work out, think of what you're proposing. A YOUTUBER ONLY server? What defines a "YouTuber"? I have 75 Subscribers, does that count? No! I haven't even uploaded in half a year. Does 1,000 subs count? No idea. They would have to have some sort of standards, which would exclude anyone who can't or doesn't meet that.
The MCSG servers runs off of donations. While many large YouTubers wouldn't mind spending a few dollars a month to play on a server, they don't have to. They could just go on another server, or even make their own (or have their fans make it.)
However, you could argue that they would attract players to MCG which would then increase donations that way.
Have you ever seen someone propose donor-only servers? Well, I have. Several times. And each and every time, it has been turned down.
These would be rather different, but the same idea - exclusive servers for only those with special privileges or ranks/fame.
It's simply unfair. What about people who are well known but don't have YouTube channels, or can't have YouTube channels due to laggy computers or slow upload speeds.