Since this is a wish list so to speak, I'll just put it all out there

Migrate all current fuel and coolant configs to recipe style data packs. One recipe type per generator.

Convert the reactor to data pack as well so that all current inputs can be overridden and new ones added.

Ideally coolant configs should be by generator type allowing different values in the reactor compared to thermo gens so they can be properly balanced separately.

Adding to this. Fluid support for heating the reactor (redstone/coal) would be good too.

Another thought for the Reactor, it would be great to be ale to tune the burn rate of fuel. I suppose that could be done by being able to specifiy some form of base energy density, however.

Also, recipe support for solid coolants :D those don't appear to have any built in configuration currently.