I feel that I might not want to join in this conversation, but I guess I'll just answer your question here...
The best way to do it is to have a prompted resource pack connected to your server. It causes all players logging in to download it and apply it immediately. It can be a bit of a hassle for the players FYI. But they would still have to be using Optifine in order to see the models. Perhaps you could use a mechanism to ensure that they are using it: whether it'd be a command system that checks their client (if possible); or simply have a room with a sign (or wall) that only displays its text with said resource pack on with Optifine, and they would have to enter the text into something to be sent into the main server.
Just some ideas. Might be good, might be awful.
Some helpful links:
Thank you so much!