I have a suggestion, to not get rid of fusion power. Instead make it high tech science and extremely expensive, but otherwise the same as a kind of unlock for late game. Expensive as in both the technology and the recipe.

This way RTG would still be useable for a while until you can earn fusion generators and they would feel expensive through resources required.

This would probably be more work in terms of balancing and compatibility with other mods, so it's just a wishlist of sorts.

The goal of this mod is to replace the unrealistic fusion reactor with something grounded in reality.
As u235 rtg internally still is the fusion reactor any mods dependent on it will still work.

Real life RTGs of that size produce something like 100 watts of power, so there's that. Real life fusion reaction produces gigantic amounts of ionizing radiation, so if you were to wear a fusion reactor on your back you'd get radiation sickness and die on the same day.

Factorio physics makes no sense. On other news, grass is green.

Equipment power numbers are ridiculous to begin with. One Exoskeleton requires 200kW, a Mk3 Assembler requires 210kW.

When trying to rebalance equipment power consumption bot charging becomes a massive problem.
Either they would have to have their power consumption reduced to the point where it utterly breaks the bot balance for stationary roboports or charging from equipment roboports takes hours.