Bad............several reasons spring to mind. The main ones are will the powder actually stand up to the temps. involved?? Most powders are cured at about 160-180 degrees. The biggest problem that I can think off though would be the masking required. The powder will go everywhere when it's applied. You'd need to be 100% you covered all the bearing housings, but more importantly the oil ways.
...also, what kind of insulation would it provide to keep heat IN the engine? I know thay're cooled by oil/water rads but there's also a lot of heat which escaped from the engine casing. Whether neglegible or not I don't know, but just a thought!
AK's done a few, the one most have seen is the tri colour one in crackle black.
The prep work took ages tho (some parts, even when split down took over a week of evenings each, to get prepared!) . Drop me a U2U & I'll give you his number to chat about it.
But as Nelly says - hope you have lots of time & patience