strangeland said:

How about putting the 'Erebor' prologue later, giving Throin a badass mystique until his backstory is revealed by Balin.

If any of the Erebor scenes are retained, I think that Thorin's should be cut from them. The fall of Erebor was supposed to have been a long time ago, but Thorin does not appear to have aged a day since then when he meets Bilbo.

He and a couple other dwarves look too human but Thorin can not be easily replaced or ignored. His appearance could only be explained (retconned) as being because he is a young dwarf.