Okay, so that means we're working with base stats. 
 
Obviously, gonna need some high base speed, def, and spc def. I really don't like doing the number crunching so I'm not gonna suggest any specific numbers, but I'd say speed needs to be highes with Def and Spc Def being secondary. A design would be nice to help assign which of the two defenses may be offset, but we don't have that atm. 
 
Other out of ordered thoughts- 
this pokemon needs these moves: 
Reflect/Light screen- obviously to up Tanky-ness 
Iron Defense 
Curse- stalling for curse to kill or force switch 
Haze- ghostly vapor reseting stat boosts is totally legit. 
Night Shade- Like blissey/chansey, has a good move to use that doesn't rely on its terrible atk stats but still has immunity to worry about 
Rock Polish- the fast keep getting faster, as usual. 
Magic Coat- fits steel/ghost perfectly as does v 
Mirror Coat 
Bide 
Perish Song 
Taunt 
Recover- perhaps 
Spikes 
Doom Desire 
Mirror Shot 
Flash Cannon