So out of curiosity wouldn't it be possible to allow Players to share with their DM in the same manner that the DM shares with the player, where in the case of a player being involuntarily removed from the session their content is removed with them, so as in to keep with Roll20 TOS where each Player/DM chooses who owns and has access to what each Member Owns. This would allow DMs to share with other DMs as players when one is missing some content. I will understand if Roll20 will choose not to make this a thing however I believe that if you make Compendium sharing not just DM to Player but Player to DM your sales will rise on the individual member level because there are players that are hesitant to make a purchase since as a player it'll only benefit them and not the group. There is also adding a friends list with friend Compendium sharing, just to give your site a bit more flexibility while maintaining TOS.