The underexplored value of early segmentation was the discretionary segment level permissions enforced by hardware.
Years ago I prototyped a system that had filesystem permission support at the segment level. The idea was you could have a secure dynamic library for, say, manipulating the passwd file (you can tell how long ago that was). You could call into it if you had the execute bit set appropriately, even if you didn't have the read bit set, so you couldn't read the memory but could call into it at the allowed locations (i.e. PLT was x only).
However it was clear everyone wanted to get rid of the segment support, so that idea never went anywhere.
Years ago I prototyped a system that had filesystem permission support at the segment level. The idea was you could have a secure dynamic library for, say, manipulating the passwd file (you can tell how long ago that was). You could call into it if you had the execute bit set appropriately, even if you didn't have the read bit set, so you couldn't read the memory but could call into it at the allowed locations (i.e. PLT was x only).
However it was clear everyone wanted to get rid of the segment support, so that idea never went anywhere.