It seems the currently offered set of Plasma Active is a bit old, and not well integrated. So I would not expect much of it. Doing this integration bit will need someone to sit down and work on it. I understand that the Kubuntu team has plans for that in the coming cycle, so maybe, just maybe, there will soon be something more fresh, more complete to play with.
The actual exercise would probably be more of a packaging-and-integration effort than cross-compiling. Most packaging systems make cross-compiling rather easy nowadays (though I have to say that I didn't try this for Debian, it certainly is easy for Mer).