While BasisOpt has been designed to be a flexible and easy-to-use tool for automating basis set optimization, it would be impossible to produce a framework that is applicable to all of the innumerable optimization strategies that could be used when developing new basis sets. One particular example is that the BasisOpt framework makes it difficult to re-use results from previous calculations in subsequent calculations during the same optimization, as might be useful for particularly expensive methods. There are workarounds for thissuch as by saving densities to file and pointing the next calculation to them -but there is still an associated overhead that would not be incurred if the optimization was able to be performed natively in a given quantum chemistry package. Another potential issue is keeping backend wrappers up to date with the ever changing code bases in the quantum chemistry community; this is not a unique issue to BasisOpt, however.