A system that I've seen done before was that if anyone went inactive for a long period of time without warning or explanation, their characters would go to the GM and would normally be killed off to A) Help hammer home the point that this was a life or death situation and B) To make room for new characters/active players. 

Just a thought. 

I'll also do a bit of a character sheet for NPC Captain Alexander. Just encase you feel like using him for something down the line. I'll write it up sometime tomorrow.