First off all. Ezio is NOT a "wuss". He is a highly skilled assassin and would put any of Skyrims assassins to shame.
Secondly, the Dovahkiin can't be in any cross over game for the simple reason that the player creates Dovahkiin any way they see fit. Dovahkiin doesn't have a standard "look", can be either male or female, can be one of 8 different races, etc.
They could certainly use the model for Dovahkiin seen in the game's trailer... but it just wouldn't feel as personal or epic.