Agreed about sixth party member and hanging tight. At level 15 or so it seems like I have so much cash and nothing to spend it on.
Upgrading party members could be cool, or introducing rarer body guards with 3 traits, or maybe a special ability I can activate to give me something to do other than incrementally move toward my fencing pro as he cuts a path through the zombies...
In any case -- fun game. Enjoyed lots.