Doesn't the plasma applet support a centralized repo for those plasmoids?
Yes. Applets can be downloaded through "Get Hot New Stuff" but that only works for scripts and portable binaries. Things like C/C++ can not be downloaded like that because they would require compiling locally. Those are the plasmoids that should potentially be packaged for Fedora if they are useful.
-- There are 10 kinds of people in the world: Those who understand binary and those who don't...