Skip over this if I'm teaching you to suck eggs, but you could have a look at the standard equations for temperature and pressure correction for power. This will allow you to asses what the various standarsd agencies (DIN, ISO, SAE and JIS) consider to be the variation of power with atmospheric conditions, so you can do some simple modelling of what the power (and hence torque) variation through the transmission might be without resorting to complex performance simulation. I did a quick Google and found the equations in this article.
I've voted yes, because I know that cooler air results (in theory) in more available oxygen to burn and also negatively affects the tyres grip on the road. However. the temperature terms in the DIN and SAE equations suggest a correction factor of about +3.6% for a 20 degree drop in temperature, which is a significant amount, but whether or not this is enough to always make you break traction kind of implies that you are almost always within about 4% of the limit of grip which doesn't sound very likely to me. Its also a big temperature drop. I would speculate that 20 degrees off your tyre temperature would have a bigger affect than 3.6% more torque.
For engines today you might need to take into account that a modern torque-based ECU might not care one jot what the ambient conditons are, as it will turn the pedal positon into a torque demand that it should satisfy without "overshooting" the mark, as it were, so you might not have to design in a torque overhead to account for variations in atmospheric conditions.