More things for the future!
1. Implement the remaining SMART normalisation of tf-idf weighting scheme.
There's some work already done on "max" normalization and we have a PR opened here.
As for rest of the normalization i.e. "fourth", "cosine" etc., it might require making changes to how matcher handles certain things in Xapian.
2. Xapian-Evaluation Module
We would want to take the opportunity to see whether we can get this evaluation moved into the main Xapian repository.
Also, to see if there are any changes required to be made so it becomes easier for interested people to use it in the future.