I could see that working.
There is a weird part of me that thinks John Cusack could do it. But I'm not sure he's got enough...I dunno...gravitas. But there is something about he and spacey...they almost even have a similar look, to a degree. Not too much, but just enough. And Cusack can play a dick.
It'd be something where I'd like to see someone stand in for Spacey on a smaller scale in a season 6, and then maybe write the character off.