It's a strange request... you didn't define much, but this does what you ask... or should... you'll need to use
another plugin to precache and AddFileToDownloadsTable the models and materials...
I tested this plugin with just me, so let me know if it doesn't work with others.
put the forced_skin.txt in your sourcemod/configs folder and edit it so it reflects your desired steam ids and model paths.
It's not finished, but if it is going down the path you want, I'll finish it.