Here are some ideas 1) a underwater area that to access you need to have some kind of breathing helmet 2)flashlights 3)different specializations like cooker, zombie hunter etc that let you improve some useful abilities regarding that role 4)new infected pacific animals that if you kill and eat their meat you get a random effect 5)a way to build a rustic cheap home with different materials that you can ghater from Auto respawning buildings 6)the ability for zombies to destroy your base overtime if they are a certayn number 7)a defense system that protects your home from getting destroyed by zombies 8)soarting food ,that may go bad, into a type of block 9)natural disasters like sand storm, some kind of infected gas in towns that to avoid you need to get in structures, earthquake 10)rustic public type of trasportation that happends like once in a mc day 11) occasional hordes, some bosses can spawn if in the hordes there are (numer+) of zombies