Lopy to Lopy - direct or via gateways?

[securigy]

Supposed there is a scenario with no Internet in vicinity of dozen of miles...
and I'd like to provide communication between multiple parties (20) carrying mobile LoRa devices nodes.

1. Is it wise at all to look and provide communication mode where Lopy talks to Lopy? (since it is limited to a few hundred meters)
2. In the above case will each Lopy see all the messages from all the rest of the participants (19 of them)?
3. Would it be more wise/efficient to have Lopys communicate via pre-installed in-range gateway/s (although gateways are not connected to the Internet since there is no Internet).
4. If the answer to question #3 is 'yes', how is it supposed to work? Gateway receives message from LoPy #1 and sends it to the rest of the Lopys (all 19 of them)? and so on for Lopy #2, 3... 20 ? In this case the messages probably should be filtered based on user preferences. The user of Lopy #1 may decide that now he want to talk only to user of Lopy #14 and discard the rest of the messages...or have an interface similar to email or instant messenger...