I like the idea, but only on Ampco brass nipples.
Drilling out the nipple cone does result in significantly higher impact force on the explosive material, so reliability should be very high. The down side is that the strain on the nipple tip material is also much greater (same force over smaller area = higher strain), and they'll mushroom much faster. The Ampco material is very resistant to plastic deformation and so should last substantially longer than stainless steel or OEM steel.