This was going to be a released but was unfinished and turned into something new. I can't tell you because it's coming. Well, it's here Scratch MW-ADVANCED-MAKER 

It was now called the Advanced maker. The reason why is to complete the storyline coming soon. You see thinking up a title with modern warfare in it would be tough to think if it was a creation game. 

That in the map Block Arena There's a skull drawing and below is a note, "Da Ghost"?

This is leading to a lore thing, but more of a secret also.

This map was added somewhere between version 0.4, but in version possibly (0.6 0.7) There's a map called "Unbanked"? It's looks like the captains waters map but it's broken and it has caution tape!