Do yourself a favor and look at the problem with a different perspective. Spend a small amount of money on an aluminum front suspension bicycle - see "Note 2" at end. Make sure it has a mid range gear system and a good set of rims for example touring rims; I'm very happy with my AlexRims G3000 after heavy use (125+kg weight with gear, forest roads at night hitting tree roots etc). Check the model doesn't have known problems by searching online - in my youth I cracked a Specialized downhill bicycle (expensive bike) and the manufacturer gave me a new frame because they said it had a known weakness. Choose a standard thing so you can put standard racks etc on it. Make sure it has a standard Shimano cartridge style bottom bracket because this will save you a lot of maintenance. The price:performance ratio of Shimano mid-range products is excellent. Japanese companies tend to make very good small precision things. I would say initially that cup and cone wheel hubs will be fine. If you want something more fancy you can always upgrade after a year of use.
Then buy some basic maintenance tools for your bicycle (basic hex driving tools and tools for changing the tires as well as a cheap spoke tension gauge and the relevant spoke spanner; you don't need a truing stand, only patience and a marker pen or chalk) so that you can change the brake pads and keep the thing running straight. This knowledge combined with the tools will save you a lot of hassle and money in the long run. There is not going to be a massive difference between an expensive aluminum frame hardtail and a mid-range aluminum frame hardtail, at least not a difference which a non-pro will need and sometimes the expensive frames are weaker because they are aimed at more specialist riders who apparently won't ride into tree roots so the manufacturers shave off material to save weight (grams). Also buy 5 bottles of the cheapest household oil you can get from the hardware store and hide these bottles around your daily locations; then use them to oil your chain very often.
Mainly what seems to happen is the cheap bikes are steel which makes them very heavy and extremely strong but also prone to rust and you want to avoid that but once you get into the aluminum framing you don't need an expensive thing to have a reliable thing and benefit from the lighter and rustproof aluminum frame - which also happens to be a bit more flexible than steel. The expensive components will break or screw themselves up just as easily as the mid-range components so better to get mid-range and the tools to maintain them along with the knowledge. Also can you explain to me the benefit of an expensive derailleur compared to a mid-range one? Whatever it does better I don't need because the mid-range ones change the gears and as far as I'm concerned that's what I need it for.
I've ridden thousands of kilometers on cheap bicycles with a lot of weight loaded onto them in camping supplies and camera equipment and I can tell you a cheap frame with good straight wheels is going to be a lot easier to ride than an expensive frame with wheels that are not true so focus on the practical side instead of the glitzy side. Tools keep bicycles working well more often than expensive components and you get a real diminishing performance improvement once you start buying stuff above the mid range.
And definitely know how to do basic bike maintenance if you'll be on fire roads.
TLDR; buy mid-range aluminum hardtail or trail frame with locking rear suspension. Learn basic bike maintenance tasks and get the necessary tools. Get touring rims. Spend 80% of your money on the right frame and rims. The rest of the stuff can be easily changed.
Note 1 - rim brakes in freezing temperatures; my experience is quite extensive in sub-zero bicycling and I've only seen my rim brakes freeze once around negative 12 Celsius. The bike was parked in these temperatures for 2 days and when I went to use it I had to pull on the cables with my fingers to loosen them from the frozen water which I assume was in the cable sheath. After that they worked somewhat satisfactorily and didn't freeze up over the hour ride I did - I think they will not freeze as long as they are being used. I had the arm-return springs set at maximum tension beforehand and the pivots Installed at their outer index which helped. I guess pouring hot water onto them would have broken the lockup. Like I said they didn't freeze during use and I think it's unlikely they would freeze during use except in very cold temperatures. I don't know about disc brakes in freezing temperatures but all automotives use hydraulic disc brakes and they don't seem to freeze so maybe that's a better option for the cold - maybe someone who knows can tell me. I prefer rim brakes because of the simplicity of operation and the availability of replacement parts and because I think the disc of the disc brake system is somewhat unfriendly. The hydraulic system also has a weight which is more than the cabling of the rim brake system.
Note 2; hardtails are best for commuting. Bikes with rear air suspension are best for trail riding, but cost more. If you have the budget then apply what I wrote but get an aluminium frame with a locking rear air suspension unit and you'll be very happy commuting and on the fire roads. Locking front suspension is probably less critical in your case - a bouncing rear shock really absorbs a lot of your energy on tarmac, not so much with the front suspension because you can shift your weight backwards and it's not aligned with the throw of your legs. You don't need to have the best rear suspension from the start because as long as the frame accommodates a rear suspension unit you'll most likely be able to upgrade it before you realise you want to upgrade it.
Note 3; consider second hand... But make sure the frame is absolutely straight and bargain like a gypsy (it's only polite).
Note 4; if you're under 1.8 meter tall then get 26 inch wheels so you can easily reach curbs etc with your feet during a commute and be nice and responsive on trail; smaller diameter wheels turn more easily because they have a lower effective moment of inertia. If you're over 1.8 then get higher wheels.
Note 5; changing wheelsets. Forget about your reluctance to change wheelsets. With a quick-release skewer it takes under 3 minutes and gives you have a much better (and safer) bike for each terrain. You'll anyway want a set of spare wheels for the day you need to get somewhere quick and realise something deflated overnight.