Introducing two kinds of "PNDs" is just going to make things more complicated IMO.
I would leave packages that have dependencies stay as .deb and PNDs totally self-contained.
But what does "totally self-contained" even mean? If you use bash, perl, python, java and ruby, do you have to include all of them and their dependencies? Do you want to statically link against
all libraries, even libc? Maybe you need to include a copy of the kernel too, just to be sure...
"Totally self-contained" is not an option. There have to be at least
some dependencies. On the Pandora, there were plenty of deps, but they were implicit, which means the firmware cannot really be upgraded without breaking some deps and thus some PNDs. That is not a future-proof solution in the long term, and it is the main cause of headaches for firmware maintainers.
My proposal is to make it explicit what the deps are, so the deps can be handled in a sensible way. It's an extra feature -- you don't have to use it if you don't like it. But if you don't declare deps, you don't get to complain if suddenly your PND no longer works on a virgin firmware since you were depending on something without including it or declaring it.