A big problem in multiplayer, both in single player and PvP servers is that there are little to no points of interest. Sure you and your friends could get in a truck and head off to Louisville till you get bored or you could join a PvP server and survive early game to hoard loot till in your base. But my idea would add both flavour to PvP and a reward for endgame teams (i will talk about singleplayer implications later on).
That Idea is a Hydroelectric Power Plant (tl;dr at end)
So somewhere along the Ohio river would be a hydroelectric power plant. The main premise of it would be that it would produce large quantities of electricity and power chunks across the map. It would be initially disabled and rundown, swarming with zombies and be relatively far from any major locations. It would require high levels in electricity (giving the skill a use) and metalworking to slowly fix and repair with the help of all that scrap metal you find across the map. In multiplayer servers, this could allow for a lot of implications. In PvP servers, you (or your team) could try and take over this power plant and hold it down from raiders. Or the people controlling the powerplant could force other players to trade goods in return for power, or have it subsequently cut off. This would add a fun power dynamic between players, a reason to travel around on PvP servers, co-operation between friends (groups could split-up, with one half providing power, while the other half uses this power to easily traverse and conquer the whole map), and a fun POI for people who want to just fight it out. The powerplant, when activated, could also bring in nearby zombies due the disruption in the environment produced. This addition wouldn't be too far fetched as in real life Kentucky, there is a hydro electric power plant that was also built before the games starting date.
Potential Problems (including singleplayer)
Adding a hydroelectric powerplant, visually, would be a challenge. Now the developers could just add a dam across the river and call it a day, but the lack of movement in water and height differences may look weird (at least I think it would). This would most definitely make it a way to travel across the river, which inturn with the already slow game development time, would mean that for a feature like this to be added, the opposite side of the river would have to be finished (which may be in progress as the developers have teased us by adding a half bridge across the river). Another problem is how the power from the powerplant would be given out. It could work like the safehouse system, where you just right click a safehouse or a chunk, and if your faction is in control of the dam you could power it. Or it could require a surface/below surface (which could work with the new basements coming up) power system to connect it, which would limit the range of the powerplant (which would also add further desire for players on PvP to head towards each other). The biggest problem with this is singleplayer. Singleplayer is already pretty boring once you make it to endgame as you can live sustainably for an essentially infinite duration and with infinite energy would dramatify this problem. The power plant could also be very challenging to get up and running in singleplayer, which could be dealt with by allowing players to change requirements in materials and levels in the settings.
TL;DR
A hydroelectric power plant in the form of a dam similar to the real life one in Kentucky that would give high amounts of power across the map (there's a lot of depth, you should probably read the whole thing)
