The problem you are fixing to butt heads with is maintaining the alignment of the repaired section with the other three wheels. The heating and cooling of the strut tower structure during the welding process will undoubtedly alter the shape and dimensions of the strut tower. Metal grows and shrinks as it is heated and cooled, and it tends to keep the shape it was in when it was heated. A frame alignment machine will be required to insure that all four wheels are in proper alignment, and that will take some expensive labor.
The steel that the strut tower is made of isn't just ordinary sheet metal. It will be a high quality, high strength alloy that may not be easy to identify or obtain. These unibody cars use the thinnest, sheet steel that they can. That enables them to make the cars lightweight, which improves performance and economy. However, it requires the steel to be much stronger that just plain sheet steel of the same thickness.
The repair process would involve cutting out the same section on a car with no rust and no front collision damage. Then rusted area gets treated to that it won't rust again, and the replacement section gets welded in place over or under the rust damaged area. If the damage is in the area of a mount point for the strut or lower control arm, this isn't going to work well at all.