I don't think you'd need entirely new ribosomes, assuming the new bases are relatively the same size as ATCG. What you'd need more of are aminoacyltransferases,

I don't think you'd need entirely new ribosomes, assuming the new bases are relatively the same size as ATCG. What you'd need more of are aminoacyltransferases, which load amino acids onto tRNAs. You'd also need new tRNA's (probably not super hard), and I imagine you'd want new amino acids. But we don't even know how to predict how existing amino acid chains fold into functional proteins, so I'm not sure what the goal of making new amino acids would further. More likely, the new bases can be used as a higher-density data storage medium for those folks interested in making biological data stores.