I would lie if I put "not to be an ass" up here so I won't.
But I'll take some of that wind out of your sails
First of all, you'd have to find exactly where the models are stored, then how they are accessed on the world map, make a new model, inject it, make the game recognize it, eiter replace an existing entry and change how it's used, clone the balamb garden mobile functions, and so on