This can be easily done using a mod. The problem is that chances are some worlds don’t have enough Sims living that world. If Sims living in other worlds are prevented from appearing, then the game would need to generate new random homeless Sims to use as visitors. Personally I don’t want the game to constantly generate new Sims. Also, since these randomly generated Sims are homeless, they would be able to visit any worlds, which again causes the same problem of seeing the same Sims in every world. If you also prevent homeless Sims from appearing in worlds, then the game would literally need to generate new Sims every time you visit a lot.
