There are a few high end industrial cutting machine manufacturers (MG Industries, Koike Aronson, ALLtra Corp, Esab) that full rotating beveling plasma machines. These are all pretty big machines that can real time bevel to 45 degrees....they have the capability to pierce at a bevel. Generally they have industrial plasma torches that can cut at up to 1000 Amps....so straight in piercing isn't usually a big issue for them. I'm not aware of any entry level or hobbyist level machines that can tilt the torch like you say. There's no real reason why it would'nt work....although it may be cheaper and simpler to just get a bigger plasma to pierce thicker material...or do your piercing with oxy-fuel...then start on the oxyfuel pierce hole with the plasma.