OK kids, lets all play nice!
Here is my out look on things; AR did not pick a Legends specific tire. The same tires have been used on dwarf cars for years with good results. INEX looked at them for that reason. If you read about Legends Car history, they originated from the Dwarf Car chassis built by the Dwarf Car Company.
Softer tire compounds would be better for grip and speed, but will not last as long on dry slick tracks, or tracks with a lot of rocks. Sharp rocks are a very real hazard to the bias ply tire. Hell, any tire for that matter!
Mixing bias ply tires and radials are not recommended by any manufacturer that I am aware of. I think that INEX will apply the same rules to the dirt tires as the pavement tires... No mixing.
Tire stagger... Bias ply tires will grow more than a radial tire. You can mess with them a bit just by using the old sun trick. Overinflate them a bit, set them out in the sun for awhile and they will stretch some. Works with the radials to a lesser degree because of the heavier construction of the tire.
We can speculate all day long. In the end, it will come down to whatever rules INEX applies to the tires. Since they are not out yet, we will just have to wait.
Steve