Hi Kevin;

Traditionally the drive floor joists ran longitudinally and the aisle joists ran like you have them. However, the barn door is the most likely place for the sill to rot so with your plan future repairs of the sill at the barn door will be easier (unless the rot extends under the posts beside the doors!). Use a rot resistant wood within 18" of the ground. (Can you tell I do a lot of sill work!)

I like Craig's layout too. The framing does not tie all of the sills together but the floor planks will do that.

Venting a crawl space is still a controversial subject, but I would do it. Don't forget to make an door or hatch to access the crawl space.

Is your root cellar o.k. on an outside wall?

I do not think you need braces back toward the main foundation in the "forebay".

Any chance you will want to waste some space with a stairway to ground level in the "forebay"?

Best wishes;
Jim