Do you think sasuke will use the hokage against the village.If sasuke decides the first hokages word don't change anything and attacks the village anyway.
And how will Sasuke take down the edo version of Hashirama?I don't think so.
Hashirama won't allow it.
Sasuke may need to take him out first, if for some reason, he decides to do what you stated.
Oro may be able to undo the edo tensei and seal them back. Unless hashimara manages to escape.And how will Sasuke take down the edo version of Hashirama?