I think this works ok if your library is something like Django or Pandas that people are building their project around. But it makes things exponentially more c

I think this works ok if your library is something like Django or Pandas that people are building their project around. But it makes things exponentially more complex for libraries like pyarrow or fsspec that are normally subdependencies. Imagine trying to do things like import pyarrow14, then if that failed try pyarrow13, etc. Additionally, python doesn't have a good way of saying "I need one of the following different libraries as a dependency"