The Liminal Hotel area that is connected to Level 0. Maybe have the finished lab area where you walk out of the async door

Each surface should have its unique sounds so when I walk on carpet, it should sound like I am walking on carpet, not like I am walking on a plywood floor. When I walk on concrete, it should sound like concrete. When I walk on metal, it should sound like I am walking on metal. You get the idea.

add vol one area

Add the poolrooms

level 999

level 94 and level ! and lastly level 3999

u should also add level 52 and level !-!
just more suggestions

add level 0.1 and 0.2

what about level 3999 the true exit so you could make a little exit from Async and 3999. 3999 has a section where its a glass door to front rooms so you could connect the 3999 exit to near Async.