I like that idea. Are you thinking of a work shop for hand tools only, and going somewhere else with the tractor?
Call me crazy, but it will still house my Kubota, Polaris side-by-side, and ATV. I will also be setting up a workshop area (something I couldn't really do when it was just a dirt floor). The upstairs loft may be just a studio or a safe area for guests to spend the night (rather than in tents around the bonfire, and risk an encounter with a black bear in the middle of the night).
It is making me rethink some of my plans in the barn. I was planning to put storage cabinets/shelves, workbench, etc. Now I'm going with a strategy of "nothing stored on the ground", so all the floor isn't covered up. My workbench will either be a mobile bench or anchored to wall like this: DIY Project: How to make a workbench
Then, without a bunch of junk on the floors, I can just take an electric leaf blower to quickly clean out the barn.
Personally I think 6 or 8 is to far to go on a work bench without some support in the middle, especially with 2x4s, as the guy in the link did. That would not be sturdy enough for me. Might holdup just fine, I am just paranoid.