People often think that any problem with a pizza can be solved by changing or tweaking the dough recipe when, in fact, the problem lies elsewhere, as in the medium used to bake the pizza (e.g., stone, screen, pan, etc.) and/or the oven and oven configuration and bake protocol. To give you an example of what I am talking about, some time ago I thought that it would be nice to come up with a version of the basic Lehmann NY style pizza that could be baked in a pan. That meant not having to use a stone, which I normally used, or having to heat up the stone to high temperatures, especially in the often unbearable summer months in Texas. In my case, I intentionally decided to use a dark anodized cutter pan, which is a wonderful pan that I purchased from PizzaTools.com. That pan also can be used to make other types of pizzas, such as a Greek style pizza (more on this below), a crispy cracker-style pizza, and even a shallow Chicago deep-dish style pizza and possibly an American style pizza. So, adding a NY style pizza to that list would have been a nice thing to be able to do.
As matters turned out, I was not happy with the results. The crust flavor was fine but the texture and external characteristics, including degree of crispiness, were not. I gave considerable thought to how I might fix the problem but the changes to the dough formulation that I concluded might have worked were such that they would have converted the Lehmann dough formulation to some other style. So, I did not pursue the matter further. However, eventually I was able to modify the basic Lehmann NY style dough formulation to be used in a pan--again a cutter pan--to make a Greek style pizza. I modified the Lehmann NY style dough formulation a bit (but kept the high hydration), increased the thickness factor to a value greater than for a typical NY style, and I used oil in the pan to allow the bottom of the crust to "fry" during baking. I also allowed the skin to proof in the pan before dressing and baking in order to give the finished pizza a taller crust with a soft interior and increased crispiness. The final results differed materially from a NY style even though the formulations were quite similar. The recipe I used has gone on to become one of the most popular Greek style recipes on the forum. I don't know if what you are looking for is a Greek style pizza, but baked on a flat pan, but you can read about the modified Lehmann NY style dough formulation I used and the finished results I achieved at Reply 20 at http://www.pizzamaking.com/forum/index.php/topic,691.msg27482.html#msg27482
. If that formulation doesn't do it for you or take you in the direction you want to go, then you might want to look at other styles of pizzas that can be baked on or in a pan. Or, you can just continue experimenting until you hit upon the desired final product.
To answer some of your other questions, yes, hydration does play a role in the nature of the finished crust, including the degree of crispiness. A good example of this is the type of crust as shown in Reply 16 at http://www.pizzamaking.com/forum/index.php/topic,5762.msg49138.html#msg49138
. As you will note from the dough formulation given there, the hydration was a paltry 36%, quite possibly the lowest hydration value I have ever used to make a pizza. You will also note the addition of sugar and oil. However, the pizza crust was extremely thin and the pizza was pre-baked (again, using my trusty cutter pan) before dressing and finishing the bake. The results were good because there was a proper balance and combination between the dough formulation, baking medium and oven protocol.
With respect to your question about the sugar, sugar will not become a significant factor in the tenderness of the crust until you get to fairly high levels, typically 4% or more. This is an area where I have done extensive testing, mainly in my efforts to reverse engineer and clone a basic Papa John's pizza. You can see several examples of how high sugar levels, and also high oil levels (I used around 7% oil for the PJ clones), can affect crust and crumb characteristic at the PJ clone thread at http://www.pizzamaking.com/forum/index.php/topic,6758.msg58195.html#msg58195
. I have not tried using my cutter pan for that style (I used a pizza screen) but I understand that Papa John's is migrating away from pizza screens to perforated dark anodized disks. I can't say that PJs will have to change its dough formulation or oven temperatures and bake times to work properly with the new disks, but they are possibilities. Again, everything has to work together to produce the desired end results.
With respect to your question about the salt, I do not believe that it is a factor, or a material one, in affecting crust crispiness. I read a lot of stuff about salt and other ingredients and I do not recall reading that salt and crust crispiness are closely or directly interrelated. See, for example, the King Arthur piece on salt at http://www.kingarthurflour.com/professional/salt.html
and the article on salt at http://www.pizzamaking.com/forum/index.php/topic,8764.msg75936.html#msg75936
I look forward to the next step on your journey to achieve pizza nirvana.