Suggested Keywork
Before I start, let me preface by saying I play killer predominately and survivor only with 1-2 friends. I also think that Moris should be changed to activate after the whole team has been hooked to still provide advantage to killer while providing counterplay for survivors.
My first suggested change is something that gets said a lot, add an opening animation to hatch. It's an easy to balance option that allows the killer time to prevent hatch plays. Skeleton Keys should have a 10 second animation and Dull keys should have a 15-20 second animation. It should not be 99-able like exit gates and generators. It should also not make the key user jump in instantly. Its true that this will allow the user to help his team after opening hatch, but it will also allow the Killer time to gain priority over hatch and close it before anyone jumps in. It may also provoke overly altruistic plays from survivors that get them killed with their teammates. Providing a loud noise notification on the key opening hatch would help with pre-opening hatch as well. Finally, I think that Left Behind should get an option to pick hatch lock if they are last man standing. Given that the Killer has 2 perks for garuented 1-Ks (Rancor and NOED), I don't see why survivors shouldn't have a similar perk to guarentee 1 escape. It would probably have to take 25-40 seconds to be balanced but would give the perk more of a purpose than having a slightly increased chance for hatch.