The wounds vs. armor value doesn't seem to hold true for everything though. A single bike goes in the vehicle category, but has no armor. But a squadron of bikers goes into the
squad category. Would a sorcerer mounted on a disc of tzeench be a vehicle? I'm not complaining, it's just sort of a funny observation. I guess if I were doing it, it would be...
single (which would include single bike mounted figs)
squad (of infantry, bikes, etc)
walker and monstrous creature (all drednoughts, orky dreds, warwalkers, giant bugs, dread knights, etc. with or without armor)
vehicle (Single vehicles, airplanes, monoliths, transports, what have you)
and strangely enough...I think an apocalypse "group" category would be neat. Like a squadron of superheavies, flyers, 101 green tide orks, etc. You could also use this as a catch all for
larger vehicle squadrons like tanks, killa kans, valkyries, etc.