System packages in (R)DEPEND?

I see packages like bison, flex, perl or sed in the system set. And i also see ebuilds depending on
them. I also heard from Peter Volkov (pva) that there where discussions about removing different
packages from the system set. So now my question is:

Should we depend on all system packages? Should we depend on some packages, because they could be
removed? If yes, which ones? Or should we leave the system packages out completly?

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Thomas Sachau

Gentoo Linux Developer