I realy am convinced that tobi did experimentend with zetsu goo on himself .... that bandage on his forehad etc .... and also tobi got hashirma dna ... i think tobi was trying like kabuto to get closer to So6p
I mean ... sharingan...rinngean... body with spareparts .... teleportation... phasing
I think tobi did not have this powers i think he somehow experimented on him to get this OP powers or got from others
He was colecting powers after all he has a lab of sharingans...
Tobi says is a former shell could mean .... that he is no longer himself .... i mean ... the eyes dosent belong to him ..... maybe half or more of that body dosent belong to him because he keeeps replacing bodyparts .... you know ..... itachi amaterasu really did hit him in full force .... konan realy damage him .... minato also hit him good... and he did remplace a hand .... who knows how much does tobi has ramplace of his orginal body ?
His body his eyes dosent belong to him they are all from others.... the rinnegan from nagato.... that sharingan who knows from who ? and the body from the zetsu parts ( zetsu goo )
Conclusion: That's why he's "No One" or former sheal because it's only his soul that remains from his former body
Note: What if that zetsu goo is a way for tobi to get immortality.....replacing his body parts..... tsunade said tobi could be imortal