You could have to create a script token to have this kind of logic. But then I am not sure you can use a script token to populate the "from" email address and name.
Not the best way to go about this, as it's a bit down and dirty, but you could create new fields in Marketo for them and use those instead of Account Owner. That way you host the marketing information you want in those fields while the fields in SFDC remain unchanged.
Then you can run a batch campaign that says to change these new fields to whatever name and email address you'd like.
It's a muddy way to go about it, but will work in a pinch.