/invopen and /ec will open a player's inventory and ender chest, respectively. However, the player must be online for their inventory or ender chest to be viewed or modified. Adding this functionality into EssentialsX would be useful for server owners.

A plugin called OpenInv already implements this as proof-of-concept.

Yes but that requires nms which we don't want to add.

Hmmm. I see. I was kind of wondering if NMS may be involved. I would suggest maybe having an automated way of determining whether or not NMS is required on a server-by-server example, yet I understand how that can complicate things with new version releases and having code that is guaranteed to break across different releases. I think, in retrospect, it is better to defer this to other plugins then.

Would be cool to see an API or something in Spigot to make this easier to do.