Well, I feel like you need to reduce the scope of this game. You’re saying that you want an MMORPG shooter, battle royale, post-apocolyptic survival game, and story-based shooter to come together?
This is a tall order, and most of these games just don’t stick together. MMORPGs tend to be more co-op, and have the capability for massive storylines and raids. I think this might be more feasible, and you can shooter elements in. However, I’m going to give some advice here:
There is no way to implement all of these and make them fit.
That’s just putting it blunt there. What you’re doing is trying to mix shaved ice, soda, a popsicle, and frosting to make a nice treat. But it won’t. It will just make a mess that you’ll regret.
However, consider picking two of these. For example, a post-apocalyptic MMORPG. That will be a base, and it will be what your game is at it’s core. Then, add these other ideas. For Call of Duty, let’s make a good gun system, along with heavy storytelling. Don’t add their Warzone game mode, nor add their gritty militaristic mechanics. For Apex Legends, you could add a battle royale feature similar to that game.
To go back to our food analogy, think of it like using the shaved ice and melting the popsicle, putting the liquid in the shaved ice for flavoring. This is your base, what makes your sugary treat your sugary treat, what defines it.
The soda and frosting can be used on the side, used together. They don’t blend perfectly, but they blend just enough to make it good and add something to the base of the treat. A nice bonus, to say the least.