Sareena
Belokk
Michael Myers
Pennywise
Sareena would've been a returning 3D era character/story mode npc (Like Tanya and Bo' Rai Cho)
Belokk would've been a "new" character (in the vein of Tremor and Triborg)
Michael Myers & Pennywise would've been the two horror guest characters (I choose these characters as Michael Myers was originally considered for KP1 & Pennywise could've been a promotion for the 2017 IT reboot if the game lasted a year or two longer)