@Ced2ric 

This would be quite useful. 

I have a situation now where I am testing three of them. The main one is in the main room, second deco is in the second room. If I don't have a second one, the second room still gets faster wifi then with installing the second deco, because it uses in that case a powerline and it doesn't check what is faster(my case would be a wifi). 

If I would be able to manually select what I want, it would allow a better connection. 

I have tested this with copying big files from my nas:

- second room without second deco p9(using wifi from the main room) - 200-300Mbps

- second room with second deco p9(i am connected to the second one) getting speeds about 100-150 Mbps. 

Here I would obviously choose the WiFi backhaul instead of powerline.