CallmeMISTER
Group chat, make a group chat for all the members of the Index, or more advanced, something like tiktok... you can also give world missions up to invasions to "Dungeons" to defeat, angels, fallen and devils, or factions of monsters or other mythological tribes, moreover, you can broaden the perspective of the novel because it would be like an Isekai.
Please post your novel(s) on othere website as well because the last update of webnovel make novels readable only via the app and that cut off non english speakjers that normally make use of the auto-translation available for websites (not the best but still makes them readable) and that is (obviously) not availabel via the APP.