Just my personal idea if you agree with it great if you don’t you don’t.
On the Predators side the survival mode would work as a single player my idea would be you start in a stargazer facility with nothing but your wristblades, no bio mask, cloak etc. As each wave is cleared you unlock a crate with some of your gear in it first few waves get you the basics your mask, cloak, plasma caster. Every few levels you get a first aid kit with enough time to use it. Other weapons like net gun, Combi stick etc will also be available but it will be up to you which ones you pick up when the become available.
Fireteam survival would work like a co-op 4 players starting maybe with just a knife or at most a pistol and unlocking new gear every few level the same as the predator.
Both have a time limit to survive and will be extracted at the end. Could have a new cinematic for the predator by showing a Predator ship come in for the extraction