Jeff, I have one comment that has value only very early in the design of your architecture. Since you've made a choice of C as a implementation language I suggest that you add one more target to the list of supported platforms: standalone a.k.a. bare metal.
Yes, embedded usage is another target.
Each module in libccoin is carefully designed to minimize internal dependencies. The core data structures, address generation, script execution and transaction validation are wholly independent of any filesystem or network design.
These modules may be used on a non-POSIX flash filesystem, with zero network support, today.
picocoin (the client) requires certain network, filesystem and process features, but libccoin (the library) does not. This is by design.