There is some discussion about getting probes into the liquid cores of Europa and Enceledus. I think this would be a great thing to attempt in KSP, but the feasibility of doing this would be a challenge. I don't expect anyone to design internal structures of moons or planets. I do wonder if we can get some more specialized parts or science values from drilling into the icy bodies?
I have to play between trips for work, so pardon if I am missing something obvious.