Interesting discussion! Down under its been all about the premium cuts.We were until GFC or whatever its new name is shipping a lot to Japan,but its called wagu from 50% up. I was at our biggest cattle show a while back & an old timer who judges cattle all over the world,Calgery etc told me that an awful lot of Angus cattle got shipped to Japan after WW2 so the idea that its a purely Japanese breed is historically a bit of a stretch.
My buddy is this countries undisputed top breeder of beef shorthorn cattle,he keeps a few wagu x amongst his 1300 herd for his own table ,something in that. I buy cuts like topside & pot roast it ,sort of. I pay $20 a kg but I get "mates rates".Its an outstanding product,I know theres a whole science of marbling scores etc & crazy prices to boot .I cant justify the $$ for sirloin,My late father who ran cattle for many years said the wagu potroast was the best bit of beef he ate in his life & we had good stock that we killed ourselves. Im probablely not much help on the brisket issue BUT I find the marbling means you can cook it to medium without losing anything. It might even help a bit because all the marbled fat melts & fat = flavour. Good luck