If you have not included the last line, I probably would not have responded. I have been 'hit' by this meta package problem before and I think your idea is excellent. I hope Debian adopts it (with any changes if needed).The non-automatic thus potentially difficult question is "what is part of KDE?" Surely kdelibs. What about Qt? And libc6? (just to name three of KDE's dependencies and to show that the answer is *not* fully deducible from the dependency graph). So the maintainer will have to take some subjective decisions, but my guess is that it will not be difficult to draw the line in most cases, if not all. Sorry for the long email. Is there anyone else "worried" by this issue?
raju