I don’t understand what you are talking about, which diplomacy? As far as I know, the two features you mention were never left out, or decided not to be coded to keep the size of Blender down. Just no one ever coded them.
i read once that there was a Discussion between blender developers - before 2.44 - about adding ffmpeg to the windows version or not to keep the size down
if we had this discussion about the ffmpeg and it’s more important to many people than the things i said
then we will not have library like this even if it’s coded
the current philosophy is to promote add-ons and plug-ins that don’t bloat the core. For example, the Material library is throuth the Library add-on, currently 1.3, which provides the facility for what you are speaking of. Then, with all the free downloads available, you can populate your library with whatever you want.
Same thought is coming with Nodes - provide an API for more nodes to be plugged in when needed. Same is for UI I think - don’t hard-code in 20 different user interfaces, instead provide a facility for people to change whatever they want and keep those changes in a configuration theme file.