There are lots of mast mounting approaches. With the eave bracket, you don't need to bring the mast to the ground. I don't think there's any reason to bring the mast to the ground on a pad unless you want to make the mast free-standing in your yard. Telescoping masts are available for this.
I would not extend the top rail pipe more than one length. The top rails are meant to nest into the next top rail section when building the fence, but that joint is not meant to provide any lateral strength. And bringing the pole to the ground doesn't gain you anything - the antennas are really light. The strength you need is against wind load; that it, the wind will try to push the mast over, but the static load is really minimal. If you want to run your cables down the side of the building, plastic conduit is very cheap and aesthetically no different from bringing the mast to the ground.
Take a look here -
http://www.antennapartsoutlet.com/ - browse through what's available and that may give you a better idea of how best to exploit your building's layout.