The gold dollar is only slightly larger in diameter than the quarter. Like 1/8"...maybe less. I don't have one handy.
It's the same thickness and about the same weight. The only discernable tactile difference is that the dollar doesn't have a rough edge like the quarter. For me it takes a lot longer to have to find the edge of the coin and feel around.
Ask any american--it's easy to feel any of the previous coins in your pocket--dimes are tiny with rough edges, pennies are larger with smooth edges, nickels are larger still with smooth edges, quarters are even larger with rough edges, half dollars are huge with rough edges, kennedy dollars are gigantic.
The dollar feels like a quarter with a smooth edge. It's really inconvenient. Even the guy at the gas station (the ONLY time I ever got one in a transaction) had to take a handful of change out of his pocket and grab them.
If the new dollar were a significantly different size than the quarter, or thicker, it would work.