I still have mixed emotions in the tractor/free range/coop debate. A lot of it depends on your end goals.
Since you are going to the expense/labor of doing the bird netting over the top, I presume you have a
chicken hawk, or other raptor problem. If that is the case, free ranging would not be the best option.
For the layers, I believe a coop is a good option...with 100-200 hens, it is obvious that eggs is a priority. Combing a pasture every day on an Easter Egg Hunt would get old very quickly. They need a secure place to consistently lay for their, and your, convenience.
Most tractors I have seen are pretty flimsy...or else too heavy to easily move. If they are awkward to move, they will likely end up sitting too long in one spot. The harder they are to move, the easier it is to put it off for another day.
Pastured meat birds still need a place to get out of the noon day sun, and hide from raptors. They don't need a fine palace, but its construction details need to take into account your predator situation.
Good luck with your
project(s).