Fusion wars idea sounds interesting, but probably will take more effort than developing the fusion itself. This is how I would imagine it from player perspective (a cross between RPG and SIM):
You start with a prototype reactor, a city run by fossil fuels and you goal is to make it fusion powered.
First you need to get money to build your first power plant.
You visit investors in banks/factories/offices then you must “figure out” what each investor wants,
by looking around and asking other people about them and chatting with them.
Getting a meeting would a quest. Then after you raise money you order to build your reactor (you can build a factory later) and get someone to agree to place it there.
Then you can start raising more money, or use the ones from electricity sold to build up the presence. Fight the saboteurs, lawyers, misguided hippies, and evil capitalists.
It is possible to make this more RPG or more SIM to simplify the implementation, but still the effort seems sizable. SIM might be more simple than RPG.
Regarding PET-ROCK-LIKE projects, I don’t see what possibly can the player perspective be in relation to focus-fusion.