Have only SPI interface on a narrow band low rate chip like Lora seems not an optimized design.
That been said, if you are looking for SPI interface on flight controller, then you probably can check
MindRacer or MindPX out. Both have SPI interface available, and
MindRacer has 2 SPI buses exposed. One tighter solution is you can make a small radio module and solder it on MindRacer's preserved pads.
On communication level you seems already have everything covered. It will be an interesting extension to see.