This was a great read, and I want point out how useful it was to see editors' comments from different Indic Wikipedia communities providing some context for their situations. The "Common Issues" and "Addressing the issues" sections were also well-placed, as well as the
gaps in content and policy documentation. This handbook seems like a useful resource to help focus discussions on common issues, particularly on translation (e.g. what policy / content page gaps should be most prioritized for translation).
I can help cross-post this, if you'd like. Are there any mailing lists you want this to be posted to, in particular?