Certainly, if these birds were allowed to free range then it would be good. It is a tractor, so if it is moved every other day, there will be little damage to grass. And the birds will be frequently let out. It is not optimum, but it is hardly inhumane.
Of course, it would be great for 3 hens.
With two 4x4 floors, that would actually be 32 sf of coop space, which is 3.2 sf per bird, which is not bad. Exceeds most Cooperative recommendations. If two pullets don't make it, then that would be 4 sf per bird which is the general guideline from the pet chicken world.
Of course, how big is this coop? You will need 10' of roost space, would that take up a whole floor?
The best thing would be to build a second tractor and put 5 in each.