Basically, something I believe to be extremely beneficial is being able to spawn players in and swap between them. Each player would act as a stand alone instigator serperate to other spawned players. You could use this to check how systems work with varying players, test systems which require multiple instigators and check if single player systems can be messed with via another player. This would remove having the need to make another account, verify it as over 18, find another device, load up fortnite on both, and launch the session. Instead, you would just need a single account to have multiplayer testing.