I was doing that once but in my case it was not the best solution. I have some nodes on battery and so they don't ask for ack. I would need confirmation but I think that if my repeater is not reliable (far from gateway or somewhere with bad reception) It could add some loss on the communications from final node to gateway. I try so to test different place using this: https://forum.mysensors.org/topic/3984/nrf24l01-connection-quality-meter to place strategically my repeater.