So all I can think of is the bottom of that hole doesn't need to be purdy. So what I imagine is drill to just a 32nd or so short of breaking through then cleaning the bottom with a flat nose drill or end mill, then punch out the bottom slug. You would still drop the slug waste in the pan but hopefully its not small enough to travel. You might retrieve most of that with a stick magnetic. Hope anything remaining collects on a magnetized drain plug. Ofcourse you would need to know the material thickness at that location. A whole lot of planning before careful work plus a bit of prayer versus pull the pan.
