As technically interesting this is, it's certainly going to be surefire way to kill your compile time :-)
I am assuming template metaprogramming is so bad because even elementary data structures have to employ ton of helper types that have to be matched/deduced against gigantic list of all other types and kept all in memory, while straightforward interpretation should not need any of that. I would expect constexpr to perform similarly to interpreted languages, which should be no different than invoking an external code generator written in Python, for example.