It'll be hard without seeing your bucket to come up with a design, atleast on how it would attach to it.
Would you be willing to make a completely seperate pusher plow for just snow?
You could start by getting an attachment plate, like this:
http://cgi.ebay.com/DIRT-WORKS-SKID...hZ020QQcategoryZ66927QQtcZphotoQQcmdZViewItem
Then build from that. A curved back would be best, like Dayexco's, but I bet that wasn't cheap to have bent. Those custom curved braces behind are really nice too, but another expense to add. BTW, very nice work Dayexco.:thumbsup You certainly don't need me to build a lift for your pontoon.
You could make more of a box design with 3/16" or 1/4" flat plate, and maybe just three angles in the back. It wouldn't roll the snow as well, but would be easier/cheaper, and still would push. Something like the pic, with added braces rear and inside.(and two sides:wink2 )
Or maybe someone around has a snowplow that has the mounts damaged, and now they'de gotton a new one instead. As long as the actual blade is good you could use that and somehow mount it to the attaching plate like in the link. You could add box ends to it for more capacity too. Maybe someone from LTS with an old one................cheap?
To me building something out of an old pick-up plow seems like a better idea than the multiple welded plates idea, or motifying your bucket.
Good luck Jmac.