Yup, thinner hyd and tranny oil is a biggy.

At -42C hydraul56 is so thick it blows lines before the relief valve can respond!

We use hydraul50 in our trannys and hyd systems.
Block heaters are a must.
You might have to change some hydraulic lines as well.
Some types/brands will crack/fail or peel their covers at extreme low temps.

If the unit will be going inside and outside, condensation becomes a big problem. Use lots of di-electric grease to protect components/conectors.
Keep the chains lubed to stop the rust.

We don't change thermostats or anything like that.
We run the same hyd and tranny oil all year round.
We'll run 5w30 in the winter in the LPGs, 10w40 in the diesels.

Electrics need heaters to keep the condensation away.

We get -20c most of the winter, and -30c for a few weeks and touch the -40's once in a while.