A second player jumping in to help isn’t ideal, but it is still powerful safety net for games that aren’t accessible enough for independent play. Particularly valuable is two controllers active simultaneously, as in co-pilot mode on the Xbox. For example, one person steering while a second helps out with acceleration and braking. This would also be essential for someone making use of two controllers as one (e.g. someone using their feet on one and hands on the other).
For this to work well, navigation of the system UI menus should be covered as well as gameplay, and both controllers should be able to be remapped. Additionally, the master controller should be able to disable/enable the secondary controller quickly (e.g. via a shortcut menu). This is very helpful for things like setting up menus or getting through tricky areas with someone who is button-happy.
Also useful would be allowing the second player to take over remotely. PS4’s share play functionality is an example of this. Online communities on PC can be very supportive, with fellow guild members often setting up some fairly intensive support system for disabled fellow player, and allowing this remote functionality could be a good enabler for it.
Allowing another player to take over remotely through the PS4’s share play feature