I have used this type of flash powder and still have one of the hand held guns around here someplace. Trust me when I tell you if you mix this stuff wrong or it gets packed to tight before you set it off the result will be a spectacular, blinding flash. And it is hot enough to burn you and melt parts of a suit.
Yeah I have to agree this is not a good idea. In my Fett builds, a few people have kicked around the idea of working flamethrowers with some dubious results at best. Unless you have specific training, in controlled enviroment, adding this to a suit is just asking for a very bad accident.