LLVM IR is being changed at a high rate. While there are some weak backward-compatibility promises (older, but not too much old, bitcode can be read by newer official IR readers), new features are introduced overnight. I expect this project to be a high maintenance job to keep up with the LLVM trunk.
Maybe this would lend itself well to parsing bitcode slices (serialized LLVM IR). I've often wanted to diff bitcode produced by different compiler versions.