Conbee USB as extender?

Hi - I’ve recently ditched my Conbee II USB stick simply because it was rubbish. Constantly dropping off and losing connections. I replaced it with a Sonoff USB 3 Zigbee co-ordinator (with the little arial) and everything has been tip-top since then. The LQI scores are higher.

All except on remote part of the house. The LQI is < 5 on three devices. I have light switches - but the no neutral ones so they don’t act as repeaters / routers.

I am looking at getting a plug to repeat the signal, but I then thought, is it possible to flash the old Conbee II stick with some firmware to allow it to act as a repeater / router maybe?

Does anyone know if this is possible?

Thanks!