There are a number of mesh protocols in the RF24 library which I believe you can run on top of a LoRa radio so you can ask Google to find the details & options. There is no reason why the middle device can’t reformat the payload and send it as a LoRaWAN packet. But you will need to embed the originating device’s info in the LoRaWAN payload.
As for a LoRaWAN repeater, you’ll find extensive prior discussions about the feasibility of this - I believe the last detailed one was for someone who needed to get around a mountain for a couple of nodes - suffice to say “it’s complicated” and we’ve not seen reports back of anyone succeeding. Whereas the first paragraph basically describes a scheme that does pretty much the same thing.
I have something like that running but using nRF24L01’s for the mesh and then the centre node sends as LoRaWAN as that reaches the gateway some distance away.