I would try to avoid rim brakes for a low-maintenance commuter bike, because they're not low maintenance. And they don't work very well in the rain. They're also not much cheaper than cheap disk brakes. It's not worth the price difference.
In my experience the roller brakes are less effective than disks or drums. The roller brakes don't bite, they're very gradual, and require a lot of force on the lever to lock a wheel. Which sounds desirable, but it means they work quite differently to other brakes. I found that when I had a cheap cable disk on the front and the roller on the back I tended to treat the roller brake as broken, since it didn't seem to work at all with normal braking force. They also need non-obvious maintenance, meaning that when something eventually went wrong I had to take them to the bike shop and wait for the one guy who knew about them to deal with the problem (worn pads).
Definitely look at hub gears - the reason your generic "European bike with gears" has hub gears is that they're low maintenance and very tolerant of abuse or neglect. The modern hubs mostly work very well (search this site for copious discussions). It's also much easier to build a fully enclosed chain with a hub gear setup. Which matters a lot in snowy weather. In the other Austr-something-a we get kangaroos and Shimano 8 or 11 speed hubs in a range of city bikes (Gazelle at the high end), and at the bottom end various 3 speed hubs. The three speed ones eventually need a new gear cable every 10 years or so, the 8 and 11 speed ones need cable adjustment and new cables more often. The Rohloff end need new oil every 5000km (no, really, it says so in the manual).
It may also be worth looking at a hub dynamo setup. Yes, you pay quite a lot for the privilege of not changing the batteries in your cheap LED lights. But, you never have to worry about changing the batteries in your cheap LED lights. In practice I use both - LED blinkies on the handlebar, helmet and underseat, dyno lights above the front and rear wheels. But I never turn the dyno lights off (there's no real drag when riding), and I sometimes forget the blinkies.
Luggage carrying is a balance between weight and bulk, and how much you carry. If you can reduce your load to what will fit on a rack-top bag you only need a lightweight rack and don't have much air resistance (plus the load is centred on the bike). If you want to carry more you could use a basket, but for more people the question becomes: one pannier or two? One is lighter, cheaper, carries a bit less, but is off centre. With two you can balance the weight but you have more carrying capacity so you end up carrying more stuff.
It's worth buying expensive, waterproof panniers. Ortleib panniers. There are other, inferior brands, but unless it's an Ortleib or looks very much like one, I wouldn't buy it (just for the record, I'm a customer and don't benefit from any sales). After a couple of years an Ortleib will no longer be airtight, and after 10 it will probably leak a bit. My commuting panniers have quite a few holes at the bottom (but not at the top), and whatever is in the bottom gets wet when it rains. But they're (ahem) 20 years old. My good touring panniers (home-made Ortleib style) are 10 years old and don't leak... but they're huge and I don't use them as often.