The copied vs. mapped memory situation is the only deal breaker in this experiment. Otherwise, file format unification would be a big step forward. The PE/COFF executable file format used by Windows (and some older Unix systems) is a relational database as well. The same goes to .NET assembly format - it's a relational database too. The wheel gets reinvented over and over again.
I was thinking that one could just write a loader that goes from SELF->ELF on load. You then pay the cost on startup. Probably not worth it for one-shot programs like ls/cat/etc, but for long running programs and daemons it might be workable.