As strong as that probably is, I was thinking along much simpler lines with the X brace. I was thinking about some thick walled round tubing with about a 1.5-2in diameter ( like what is used for subframe connectors or a good strut tower brace), and the crossover point would be aft of the tailshaft of the transmission. This would facilitate removal of the transmission without a major ordeal, and allow for proper driveshaft articulation and use the X brace as a support for a custom transmission crossmember to eliminate the stock one. Plus, it would not be bulky enough to cause too many problems with exhaust placement. In theory at least.
If you look at that picture, it would be nearly impossible to remove the transmission from the engine without pulling the engine at the same time-- especially when the body is bolted on.