Regarding the AFK on the friend list, that is not really possible. The friend plugin is hosted on the proxy (so active across the network). This means that it is really tricky to get the data from SRP, and probably not worth it as it also wouldn't work on FRP, hub and events.
Adding it to the /seen command would require remaking that command, as it is currently handled by essentials.
Adding it to the /seen command would require remaking that command, as it is currently handled by essentials.