Sharp sauces suit fatty meats like duck. So, sharp fruit sauces work well, as does mustard or light vinaigrette.
But these things get lost in translation. No blackcurrant vinaigrette available? Try some jam. You see that kind of thing in Westernised versions of more exotic foodstuffs all the time. I don't think this is any different.
For me, one of the most interesting duck dishes I've had was in Hungary, with a slightly sharp, coffee-based sauce. Never seen anything like it since.