Looking at the periodic table there is lots of elements that you did not cover or skipped that imo could probably could be created from the fission process:

• Actinium (227) maybe to be created form the decay of thorium 230
• Protactinium (231) could be created from the decay of uranium 233
• The 5 remaining actinoid (level 7) elements after californium with the same progressive methods from centrifuging depleted fission fuels (im not doing this, ill have a simpler way to do this myself)

Its ok if u don't do this since im implementing this in my modpack, but just putting ideas out there that might make the mod even more immersive and progressive perhaps, even if it isnt realistic, idk about that one. But hopefully you can keep this idea for the overhaul update.

Pretty much the only reason various isotopes aren't added to the game is because they don't have a use. The overhaul branch of the mod now doesn't have Th-230 anymore, but does have Pa-233 for the breeding of TBU fuel, for example.
I didn't add the heavier elements simply because the half-lives become very short, but I know that there are people planning to add them to their own packs also :)