Whenever we define the glyph set of our fonts. It is always the same question: To decide whether or not to include a certiain character, we have to compare the additional work and the additional (language or otherwise) support.
Whether it is worth the additional effort may depend on the design, the purpose or the client. So, I would like to have more fine-grained information on the additional language support I get for a particular character, and in reverse, which (additional) characters are required to support a particular language (in addition). Ultimately, only I can decide on the character set, and I want to have the relevant information.