reminds me of zpaq [1]. It is an public domain compression tool, which save the decompression algorithm as IR into the compressed archive. It is written by Matt Mahoney, best known for the PAQ archiver series.
Without -mixing=2 (eg for the results present in the blog post), DivANS actually relies on a static determination about which models to use in which situations, serialized into the file in the mixing map. It only ever evaluates a single model per nibble.
The idea of mashing up the intermediate representation with a bunch of different compressors isn't present in zpaq as far as I know, but the spirit of the idea is similar, but on a per-bit level, rather than on the IR level.