I've had a few plow vehicles. I always had Western brand plows and have been happy with them. I wouldn't use a D2 as a plow vehicle, but If I were to, a 6' Western plow would probably be the right size. They probably don't make a specific subframe for a D2, so you'd have to fabricate one (on top of the $3500 or so for a 6' Western plow). You would also have to run insanely heavy front springs, and possibly fabricate outside the spring shock mounts so you could put airbags in the front springs. A small plow like a 6" Western weighs several hundred pounds (with all the hydraulics and such) and this weight extends pretty far out, so suffice it to say, not even the "heavy duty springs (i.e. 779s or 751s) will come close to cutting it. Your other problem will involve the alternator. You need a strong alternator to run the plow, and the D2 alternator will not be up to task. Also, the D2 is probably an automatic, and I wouldn't want to plow with an automatic.
Plowing snow is incredibly hard on a vehicle (escecially clutches), and vehicles tend to 'wear out' rather quickly. Plus, you have to install a sub-frame on the front of the vehicle to accomodate the plow which reduces the approach angle for off-roading to virtually nil. If you *need* a plow, buy a beater of a 4WD truck and use that. Your Disco will thank you.....
I agree. I don't think you "wear out" the whole vehicle per se, unless you plow in an abusive manner, but you are right in that you will go through more driveline parts than the average bear (unless you have a truck that's REALLY set up for it, like a Dodge 2500 heavy duty with the factory "plow package" [bigger alternator, stronger clutch, an already bulletproof driveline]). A Ford Ranger I had a plow on (with the old dual I beam front end) plowed ok, but it went through a lot of clutches and clutch control parts.
Bottom line - don't do it unless you have no other choice.