After reading 220/221's response, I called the electrical inspector today and was told that:
1. Existing wiring is okay without an AFCI. Do have to upgrade grounding and bonding to code.
2. The smoke detectors required for any permitted job in my area do not have to be on AFCI.
3. I can run the new branch circuits and terminate them in j-boxes under the house.
Jeff, I thought about the idea of running a service raceway, but the location where the panel is going is on five feet of concrete slab with 2x10's lifting to finished floor, then it gets into the crawl space.
Do you think I'd be able to effectively run cable through a service raceway that long (~4 feet vertical down from the panel and then five feet out to the crawl space)?