I actually do not even think that that is even a realistic option as the increase in material weight would over stress the existing structure below.Hopefully no one in OTD reads this: Your right filling it in would be the only way. Lets not present this as a "Good Idea". Keep the CURBS! (Not the temporary ones at the Candy Shop, though)
Huge theme improvement: I would like to see either brick sidewalks like Disneyland or brick Main St like Disneyland Paris. Both look really cool.