We don't event need bugs to be fixed right now (the game isn't that buggy). What we really need is missions, at least basic waypoints/triggers, and possibility to script scenarios like in Arma games. This way game will start making sense.
With entities above and a bit of scripting it'd be pretty simple to create missions like "Gather a team, find/repair a boat, and leave the island", with 5-6 boat parts all over the map, and tons of zombies in the island.
In other words - infinite possibilities.