@hanssanitizer Leaving the LoRa radio in RX mode means the LoRa chip will be drawing a bit over 10 mA at all times.
What are your constraints in terms of battery size and battery lifetime? A relatively large 2500 mAh will be emptied in 10 days in this scheme, not even counting what is drawn when the LoPy is awake, so probably less than a week overall, depending on how often it wakes up, for how long, and what it does.
If that's something that is acceptable for you, then one could probably explore modifying the firmware to handle that, though my guess the complexity will arise from having to bypass all the LoRa chip initialisation on startup.
Note that if that kind of power budget is acceptable, maybe just using the light sleep modes may be OK and probably much easier.
For reference, the original LoPy uses the SX1272 while the LoPy4 uses the SX1276. I believe the FiPy uses the SX1276 as well.