With the OAT at a constant -15°C, I don't think cold soak is your problem. This temperature will also give rise to relatively dry air, even if it is misty. Also, the fuel left in the aircraft after a night-stop won't change the need for de-icing - it will either need it or it won't. This will not change if you have to uplift fuel. Therefore two issues remain. 1. Does the aircraft's AOM preclude this sort of operation and 2. Is it economically worthwhile to do so?
Answer those and you have your answer.
PM