What if you hire voice actors for each of the characters? And level designers? And animators? At what point does it stop being a solo project? Only when outside investors get involved? Or does it only stop being "solo" if those investors demand board seats? Or can it _still_ be considered "solo" even then?
Given that Death Stranding 2 only credits Kojima as the game's writer and designer, I guess -by GGP's very silly definition- it's a solo project. XD