I haven't been back to Oblivion for a while, but I recall that there were a few more options like a replacement head mesh that you didn't mention. (Head06 by throttlekitty) Just like Skyrim, you need texture replacers that map to the heads and bodies you choose, and you could make your own using some Photoshop layer kits (also worked OK in GIMP). I did the latter, and mixed and matched layers from multiple mods.
It was also possible to use a body replacer as "clothing" to have one NPC a different shape from another when naked, and of course the clothing could include a variant body size.
Extreme example