Okay we've got to get into SERIOUS character assignments here:
WHO is going to be Agent Franks? Seriously, I liked him in the first book, and in MHV he totally kicked ass and.....well..I don't think he ever got around to taking names.
My #1 Choice: Paul Telfer. A little bit pretty boy looking, but from his NCIS appearances, can be made into a pretty badass looking dude. Note: if his acting skills are okay (I don't know) also a decent choice for Owen.
#2. Choice. Adam Baldwin could still do the role. He's somewhat out of shape (rumors say bad back injuries?), but nothing too bad, stunt doubles,etc. could work. After all: Franks is basically the badass version of Jayne in a suit.