With 2 inches of lateral movement I'm not sure where I would have an issue installing and removing other than the overall weight of the plate.
It's the overall weight of the plate that makes installation such a major hassle. A plate of this size, as Chaz mentioned, is around 45 pounds. With this kind of weight, you'll scratch the shelf if you place it on the shelf and slide it across the shelf and into place, and you'll do even more damage if you try to slide the shelf with the plate on top of it. The plate basically has to go into place without sliding, and because you're placing it inside an oven, the leverage is incredibly awkward, and can be brutal on your back. Two 22.5 pound plates are far easier to deal with.
I have yet to find a viable method for propping up the front of the plate in a manner that doesn't adversely affect the distribution of heat on the preheated plate. In order to achieve a stable configuration, you have to add thermal mass, and this thermal mass tends to insulate the areas of the plate where it contacts.
Size is such a vital component of great New York style pizza. A 17 inch pizza is better than a 16 inch pie. Launching a 17 inch pizza on a 17 inch plate is incredibly difficult. It kills me to have to recommend subtracting that half-inch for the lip, but I don't see a lot of options. You could remove the shelf from the equation and rest the plate(s) on steel bars:http://www.pizzamaking.com/forum/index.php/topic,12692.msg126602.html#msg126602
but with two plates, you'd be talking four bars, and possibly a less stable cooking surface. I don't know, if you're feeling especially strong, and want to work with a 45 pound plate sitting on two bars, that half inch of extra real estate would be incredibly valuable.
Steel plate usually comes with a layer of iron oxide, a.k.a. mill scale. While perfectly harmless, mill scale can be removed by soaking overnight in vinegar, then scouring with steel wool. While not necessary, steel can be seasoned like an iron frying pan. If you do season it, I would go with a very thin layer of oil, in the event that oven temperatures cause the oil to start smoking.