The game can be played with mouse only - you can move, fight, choose the dialogue options. But all of this a bit longer that way.
I see thank you it could work for me with turn based, I often choose mouse only despite some keys would speed up some stuff. I probably can go over the lack of rebinding.
If you really need to rebind keys you can use 3rd-party key mapping tools such as AutoHotKey.
However I agree that the mouse support in this game is great, so you probably won't even think about needing keys...