For old computers?

I guess the resource thing is why the Plasma devs are integrating as much
as possible in plasma itself, like power and network management. But as
you say, stability is the problem you get. More testing and QA is needed
to get plasma to a reasonably stable state. In case of NM, this isn't a
big issue - NM already IS a separate daemon, and having ANOTHER daemon to
just show the interface is silly to begin with...