Quote from RAT5 (my emphasis);
...the topic is about tankering fuel into a night-stop where de-icing is expected the next morning.
Piltdown Man and I seem to be alone in pointing out that de-icing in the morning may not be necessary, and is not predicated in the OP's assignment.
Quote from Ledhead27 (the OP):
I'm writing an assignment on fuel tankering and part of the brief includes the following:
"Discuss the issues with tanking when operating a return sector to a busy airfield in Germany (e.g. Munich Airport), with a late arrival and early departure the next morning. The flight is to take place in winter with the OAT at a constant -15°C. What issues need attention? What dangers to the aircraft could there be? Would there be a time during inclement weather when tanking would not be prudent?"
The assignment, which leaves many details unspecified, invites discussion of all the possible issues for and against tankering. Hence my reference to fuel prices.
The (admittedly unusual) fixed temperature of -15C overnight means the wx conditions are almost certainly overcast, and probably anticyclonic. So the atmosphere is likely to be very dry. IMO, precipitation and frost are unlikely but, as ever, cannot be ruled out.