You are going to have an issue with battery on anything you use. If you are shooting all day you need AC power to a bunch of batteries but most things will need to be powered down for a battery swap.
Also 24pN will not work with FireWire out. You have to shoot 24p (over 60). A FireStore can remove the pulldown while it records to give you the longer record times.
How long do you need to record? Under want power conditions? Will you be able to stop the record? all this info is need to give you educated advice.