I can attest to the egg switch-a-roo working but from the other way around. My sweet darling goose
Phoebe (who passed on this winter after many months of being sick) had seen the Ducks in the flock brooding and so decided to brood herself.
At that point there was no Gander, so I started switching out her eggs with the ever growing pile of duck eggs (another issue was that ALL of the ducks were laying in a single nest, they would shove the brooder off the nest, then lay - leaving their eggs, at one point I had a single duck (
Breakfast) sitting on a big pile of thirty six eggs).
Phoebe eventually incubated to full term the eggs, only one survived - two others were crushed just as they were coming out of their shells.
The surviving hatchling I named
Drew, he imprinted on the geese, totally thinks he is a goose, hangs with the geese rather than the ducks, does the aggressive/threat goose gestures (while the other ducks run & hide)... here's a shot of
Drew with the Gander (
Blinkie):
Anyway, she really never rejected him, so I think the imprinting eventually might work both ways. Though she did at times become aggressive / pecking him if wandered off then attempted to come back BUT he was determined to be with Mommy - eventually sneaking back under her... once there she accepted him as her own. Just keep an eye on them during the first couple of weeks.
Drew did start mating with another Duck (named
Lunch) but a Bald Eagle took her. After a while of him being alone (except for hanging with
Blinkie) I was stunned to see him push
Blinkie off my Goose (
Pooh in front)... then he tried to actually mount her... (if some genetic accident ever occurred what would one call it... a Guck or Doose?
). It was very stunning to see that happen.
Anyway, the only main problem that you might had would have been during incubation - egg rejection (but that doesn't seem to have happened), maybe also whether the duck will be actually able to turn the egg. You are lucky since ideally a goose egg incubating should have a cool down of 15 min a day, which I don't think ducks do.
Cheers,
Jonathan