Processing carcass in winter

[Valor]

Animal body should freeze in winter (depending on weight and temperature) in time and make it unable to be skinned and butchered after it has frozen. You should be able to carve some meat from it with great effort, but full butchering should be very exhausting task, if even possible.

[JP_Finn]

Frozen carcass should also not spoil, as long as the temperature stays below freezing.

In real life large carcasses need to be hung for a week or more to relax (from rigor mortis), and to age the meat. But that might be taking the simulation towards too tedious.
Hanging in a barn is common, and doesn’t take much heating to keep indoor temperature slightly above freezing. And yes, butchering a moose (alces alces) is considerable, team, effort.
Often takes hunting group (4+ hunters) 8-12 hours to process with modern (masterwork?) equipment.

[Erkka]

In real life large carcasses need to be hung for a week or more to relax (from rigor mortis), and to age the meat. 

That is true, although I think that the need to do so is based more on taste, not the absolute necessity of it. Proper hanging makes the meat more tender, but it is also perfectly possible just to prepare the meat right after butchering.

Been there, done that. I think YouTube also has a video of Sami and me preparing a freshly butchered lamb, but the method we used to cook it made the meat super tender despite the meat hanging barely for a few hours. And with less time-consuming methods an okayish result can be achieved with roasting birds on embers and such. So, personally, I'd say that a need to hang meat would not add that much to the game.