Well you (or someone) would need to test damage from abilities with different sets of gear, then we can find the weights.

If by "stat weights" you mean by the formulas by which they are applied, then yes, we'll have to do tests with materia (such as 0 gear, and then adding 4, 8, 12 int materia).

If by "stat weights" you mean "which stats are best for my class" well you don't need to figure that out, the point is to run the sim to figure that out for you.

Of particular note is how stats affect pets...afaik we have little to no data on that, esp on pet recast timers and how long they take to animate abilities.