I would like to see even higher tiers at even higher costs. The way the game currently is (unrelated to the mod) is that eventually you run out of expensive things to craft (Aside from the ever increasing infinite resources).
It would be nice to have a way to keep spending resources for something where the benefit stays linear but the costs increasing exponentially. This would keep it balanced as well. A way you could do this (But of course make it your own flavor if that's your preference) is like this:
Cost to craft new solar panel = (new solar panel power / previous solar panel power) * vanilla solar panel space saved
Example: you want to create a solar panel that's twice as powerful as the vanilla one (so 120 kW instead of 60 kW)
The cost would then be:
120 / 60 = 2 * 1 = 2 normal solar panels
Now we make one that's twice as strong as the new tier:
240 / 60 = 4 * 4 = 16 normal solar panels or 4 tier 2 solar panels
You could make it less exponential than this if you'd like and add in higher tier requirements like the mod already does to compensate, perhaps even adding in nuclear requirements for your higher tiers. You could make it just optional in the configuration with a checkbox or you could just throw out my suggestion out the window if you don't like it at all ;)
