What I'm missing is something like <pinheader>, just for generic connectors - say, <connector variant="[microusb,miniusb,usba-female,usba-male,vga-male,vga-female]">.

Also, for resistors, is there a chance for PTCs and NTCs? And <diode> would benefit IMHO from a variant="[zener, schottky, photo]" plus associated parameters for them.