It would be lovely to have a more accurate representation of actinide decay chains, a la NuclearCraft. I was genuinely saddened to see the absence of elements like Thorium, Curium, Californium, Americium, etc when searching them in REI. Part of the reason I stuck with older version of MC for so long was NuclearCraft's complex, relatively accurate actinide decay chains, and the (admittedly subjective) fun process of designing reactors specifically to obtain decay products further down the chain, partly for the energy, mostly for the fun of it.