Update (10/26, 3:05 PM): Today I pitched the idea to Ignacio De La Fuente and Nancy Nadel. Councilwoman Nadel, in whose district the site resides, has been receptive so far. She's passing the idea along to Redevelopment. We'll see what happens from there.
According to an article in Sunday's Trib, some of the dealerships on Broadway Auto Row have expressed interest in relocating to a new "auto mall" concept at the old Oakland Army Base. Reasons given are the location's proximity and visibility from I-880, the fact that it's a little closer to San Francisco, and lower land costs/leases.
There are already plans to build various types of housing in the area based on available zoning and planning resources, but even with those plans, there exists at least one site where a ballpark could be built. The site is at the intersection of 27th Street and Broadway. It's roughly the shape of a triangle, and is just about the perfect site to shoehorn a ballpark in. Broadway Ford, a used car lot, and some other auto-related businesses currently occupy the area. I counted 2-3 houses and small apartment buildings as well.
These residents and businesses would obviously have to be relocated, and other land in the area would have to be acquired to fulfill Wolff's concept of surrounding development paying for the ballpark costs, but the site has several advantages, including its ideal downtown/uptown location and access to BART. There would also be neat views of the Oakland skyline and Lake Merritt (presumably from the upper deck). It even has a slight downward slope that's conducive to building a ballpark. Keep in mind that the idea of a building a ballpark on the site isn't mentioned in the article, but if Wolff's looking for an appropriate site, this one may just work.
What would it look like? Compare the image above - the land as it currently exists - with the image below, which has a conceptual design on it. (Please note that the images were created with the wonderful Google Earth application.)
That's Lake Merritt and Adams Point in the upper left hand corner. The nearest BART station is the 19th Street Station, about 5 blocks away from the right field corner. The entry to the BART station is actually at 20th and Broadway. It wouldn't be possible to build a closer station because BART's tunnel makes a westerly (left) turn just past 20th Street before it aligns with I-980/CA-24.