how do i change player model in hammer editor (chell, bendy or atlas, p-body in singeplayer)

idk how BEEMOD did it, but my method would be to have a prop_dynamic with whatever model you want the player model to be, and have a logic_auto with an OnMapSpawn output to a point_servercommand. The command would be "setmodel <model path>", with the model path relative to the "models/" folder. You can also choose to kill the prop_dynamic before or after the command fires, since the model will stay precached until the map ends. This method can also be useful for some story driven maps, since you can switch player models at any time during the map. I hope this helps! If you'd like an example, I'll gladly send an example vmf.