Tobias is a freak of nature. He can do Ghost stuff, indie rock stuff and even death metal. His DM band Repugnant has a cult status in the metal underground. And now with Ghost, he's one of the biggest names in the mainstream side of metal.I think what you Point Out so negatively is what makes Ghost this great. Normally you need what? 4-10 different Guys to get some decent Songs done. Tobias writes and records EVERYTHING. Where most Bands would Stop He builds Up an Image and an ever continuing Story around it AND performs it live in a phantastic way. And His musicians get surely payed and have fun with what they do or believe me they could Not Put Up a Show Like I saw two days ago.
Also, as far as I know the ghouls are ment to be permanent members but of course when they aren't satisfied with how Things Go they got to go.
His diversity alone speaks volumes of his quality as a songwriter, to be able to create quality music in different realms of sounds is a pretty giant feat.