Solar is nice, but has two problems: it takes lots of space, and layout doesn't matter. All the best parts of factorio involve work to get a good layout. I propose a tier two solar system, with similar capacity, complexity, and space to nuclear.
There would either be a central tower that generates heat, or each panel would generate heat. Heatpipes would lead to exchangers and turbines/engines, like in nuclear power. Restrictions like limited range for the tower and line-of-sight (no tall buildings between) would lead to a variety of possible layouts.
The fact that this would give new ways to use+arrange existing items is its biggest strength. It would add depth to the electric system, so that heat+turbines feel like general reusable concepts instead of nuclear specific buildings, but with their own solar-specific problems to solve, like overnight energy storage.
