Melbourne to Sydney via the snowies in one day might be even a little more than I would be prepared to do Andi!!

Two days is comfy. Via the coast can be done in a day no worries at all. It's only about 1000klms that way. However via the snowies it's prolly gunna work out to about 1500+ klms!
As far as a route is concerned try this. Do your Melbourne to Bright run as per yr intention, then over the Tawonga Gap to Mt, Beauty, then the back roads up to Tintaldra, Elliots way, Kiandra, Adaminiby then Cooma. From Cooma, you have two or three Choices.
1. cooma-Bombala-Wyndham,Cathcart,Candello,Bega-coast to Sydney.
2. Cooma-Batemans-Coast to Sydney
3.Cooma to Canberra to Braidwood and the backroads up into Sydney.
Andi, A relatively easy ride is also to be had going Via Bairsndale Bruthen,Cann river,Mt Imlay then back to the coast and up the coast to Sydney.
Cheers

"I hate to advocate drugs, alcohol, violence or insanity to anyone, but they've always worked for me" Hunter S. Thompson.
There are really only two questions in life. 1.Which way do i go? 2.What is the lap record?