Easier Ways to create new mobs and Item Textures

In Minecraft I like to create my own mobs, armor, items and blocks but it is getting harder to create what I would like to create because I can’t create a re-skin of. Zombie to look like A yeti for example. I think it would be a good idea to add easier ways to create new things without the use of mods or optifine. Maybe I can retexture armor to be emerald armor but I am not replacing any existing armor. Same thing with mobs and items.