In reverse order, I would go for 4wd w. chains on all four wheels, and turf tires which accommodate chains better than any other tread (IMHO) ...and, if it really is flat, as you say, chains might not even be necessary (as they are for ice and hills).
Next must would be HST (hydrostatic drive), unless you can find a creeper gear and/or are good at replacing clutches. Block heaters work and I would think are a must ...I also have a trickle charger on the battery attached to the same plug as my block heater. Note that some tractors are notorious hard winter starters (Case?) and others take it in stride (Kubota/Deere?)
Another must, winter diesel fuel blend or no.1, which should be what's sold in the winter in your area...and I would use an additive to raise cetane and reduce gelling ...along with a jug of diesel 911 on hand. Depending on how you fill up, a water block filter or some other trick to assure no water in the fuel (e.g., let it sit in your containers and leave the bottom inch, or so, maybe). If I had starting concerns, I would use synthetic oil and lubes, also.
Now find a blower that you think suits your needs and look at its horsepower requirements, which would determine the tractor/HP size. Rear mount is far cheaper per inch...but means you have to look backward...if you can do it in one pass (7-8 foot blower) then that's just 1 mile of backward driving ...two passes 2 miles, etc. On the other hand, a blower on the rear means you can have a front-end-loader (FEL) on the front which is nice for some clearing, and for extricating yourself when 4wd has gotten you into trouble... it's nice for dealing with the end of your lane, where it intersects with the public road, which entrance the municipal plows have filled in for you; and, a backup if your blower gives you a problem.
I would want good work lights front and rear, which may mean a larger alternator (swap in the alternator from the cab version of your tractor...if you don't have a cab). There will be times when you will want to operate at night, I bet.
A cab would be my next consideration ...apparently not a must if you have been snow-mobiling in the past but, still...30 below is a challenge. Yes, you can add it later, but it's never perfect.
I would then make sure I knew enough to change the shear pins, wherever, and swap out the fuel filter (and bleed the system after doing so, if necessary)...getting stuck in the middle of a mile-long unplowed road isn't my idea of fun.
I couldn't see how your lane is demarcated but wands or other visible markers for early in the season would be nice ...especially when driving backwards.
As for the economics, figure out your wished-for rig and look at the (5-yr) finance carrying charges ...if they are about $6k per yr then you are about even, I reckon ...operating costs, fuel and maintenance offset the residual value of the rig after 5 years.
[Kind of a longish answer, but it's 98 degrees here, now, so writin' about snow is satisfying.