A cut-off wheel mounted to your Dremel can be used to split the outer race and it will then be easily extracted.
Other recommendations involve zapping a couple arc beads on the outer race and removing it; so say "they". Never seen it done. Another ghetto removal technique is to drill a couple angled holes through the frame neck to access the outer race. Then use a drift to knock it out. Not my style, that.
Either way, you will likely need new bearings if the outer races are even the tiniest bit damaged during removal.
Then there's the whole correct refit procedure.
Might you call and/or haul the frame to a BMW dealer and check if they have the correct tooling to remove the races?
I have Dan's complete stem bearing removal and refit tools. Well designed and worth the price. The job can be tedious but with the right tools, it's one time and done.