Yes, no, sort of.
I assume you have read the article you linked and found "How to build your own lorawan gateway", with the gateway being raspberry C.
You will also find the datasheet for the RFM69HCW transceiver which reads: "... features of the RFM69HCW include a 66 byte TX/RX FIFO, configurable automatic packet handler..."
In those kind of chips the packet size (if enabled) is fixed. If you have split-second accuracy (microcontroller level) you can get away and drive them in 'continuous mode': not something you will be able to do an a raspberry and/or if you want to maintain your mental sanity.
And anyway, even 1 KB would be huge. In general it will be a bad idea from an RF point of view. Your target should be more like 20 bytes per packet!
Your options are:
- Install a whole load of software and have a full stack; maybe some will provide big transfer features (IDK if such a thing exists)
- Get the rid of the whole LoRaWAN stuff altogether, just use the LoRa radios themselves and figure out a way to do the transfer yourself.
Fair access policies will still be an issue, maybe this could interest you.
The outlook seems quite bad to me but we could still wrap up and say yes, it can be done. With some caveats.