[1.8]Modify item model + texture, as well as entity texture

[Miclebrick]

I was wondering if it is possible to modify an existing item's model without using a coremod, and the entity textures as well. I am making a mod that is made for a server that is supposed to be able to be played on with or without mods. It works by changing these based off the display names. e.g. a zombie named Goblin would have a unique texture, an sword called Hammer would be shaped like a hammer, and have a hammer texture. Would this be possible without a coremod?

[herbix]

Server resource packs would help.