Package: 3D Armor
Using entities would make this mod much easier to be worked with. Armors are quite an important thing and I don't feel like to encourage a mod with legacy code.
You must take into account performance considerations though (5 entities per player is still a lot), the buggyness of entities up to and including 5.x versions, and the backwards compatibility of this mod.
I agree though that not changing the player model would be immensely helpful for compatibility. https://content.minetest.net/packages/LMD/epidermis/ for instance doesn't support 3D Armor right now for this reason.
Edit: There seems to be a mod that uses entities for something similar: https://content.minetest.net/packages/davidthecreator/equippable_accessories/. It isn't focused on armor though and it's code quality appears to be even lower.
@CrochetCode - Please consider the traditional MT claim of supporting older platforms.
"Minetest is coded in C++ using Irrlicht engine. Also Minetest is very lightweight so it can comfortably run on older hardware and netbooks."
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This should not hinder reasonable progress but I would hope this statement stands today and for the future.