I would stop thinking of it as first aid. I know I'm being picky, but first aid is something to get you to the doctor so that what ails you can be treated. If you're in a place like Mississippi after Katrina, you're in a survival situation, not a first aid one.

My suggestions are to assemble a suitable kit of supplies and get the training to know how to use the supplies. I've got a list of links at
http://www.cieux.com/adventureKits.html
for, among other things, how to equip a long-term kit and where to get training.

I'd suggest doing some research and building a custom kit based on your needs and situation. I'm in an area that gets earthquakes, so I going to worry about different things than people in Florida and New Orleans (burns from broken gas mains igniting surrounding buildings, for example), but many of the issues are similar (collapsed buildings, but our collapses will be of multi-story office and apartment towers).

Among the non-first aid issues are long term food, long term water, and long term shelter (and local weather). These may be more important for that long term than bandages and iodine.