This is definitely one of the best SpaceAge mods out there, however it is mostly self-contained, the infinite researches for ice melting and noble gases productivity, along with the new lab have no real use at this point of progression. Personally, I love the isotope system and would like to see more ways to utilise currently unused isotopes. (We don't need so many fuels - if ever, only the best one will be exported from the Shattered Planet). It would also be great to have a reason for exporting things from the SP to other planets - maybe additional uses for the new machines? (bonuses to productivity, speed, or a way to craft vanilla items with them - similarly to the foundry or the electromagnetic plant. Maybe upgrade the Realizer and make it viable to use on Nauvis instead of Biolabs or labs from Muluna?)

P.S. Recipe for creating liquid Americum-241 from tiny clumps is missing. It exists in factoriopedia, but cannot selected in the machine.

Coming up with ways to make the planet more rewarding is a unique challenge beyond doing something that other mods haven't already done. In short the Shattered Planet was designed to be end of your journey. Fuel values were added to all the other fuels for consistency and yes, only HEC251 will generally be exported, but even then it's outshined by Fusion Train Fuel mod or Electric Trains. Realizer is an example of a building that aims to be an alternative, not a straight upgrade to obsolete or disrespect other mods (Mulana for example)

Additional uses for the new machines like the Super Magnet are more in theme, but I can not see a use for the more specialized machines that aren't already handled by what you get from Fulgora, Vulcanus or Aquilo. They're designed solely as a limiting factor as your progression gate; that's not to say I'm not open to giving them additional uses, though actually giving them usage outside of an overhaul would be a hard pressed request, almost anything that can be done is already handled by something else that exists inside of the game.