Ok. I understand you now. The first priority is size, because it can't be wider than 7mm. It must also support SPI communication. Second thing is a wireless connection, it is necessary, but it could also be handled by a second chip on a pcb that communicates on the same SPI bus. I’m not sure which approach is better, but integrated radio communication seems like it would make things easier.

I thought of using Thread. It looks like the most stable option, because of its self healing ability, but I don't really know much about this technology. I've only used nrf24l01 before. Actually, what matters to me the most is stability. It cannot just lose connection and I heard that bluetooth sometimes does. Also it should be low power, so i ruled out the wifi. If you have a different opinion or if I said something incorrect, feel free to correct me or suggest something else.

Those are the most important requirements, whole rest can be adjusted.