I am no expert on cages but i have been readin into them alot and looking at a lot of designs. Doesn't look bad. I would probably change the design of the bar between the b pillar and the back down bars. Do away witht he horizontal bar and make it a complete X.... Also, if you get the cage back far enough you can do away with the tailgate bar and tie the 1/4's into your cage.
Also, I would do somesort of B-pillar brace also. It iwll hinder rear seat access(you said you were taking it out anyhow), but it will help strengthen up the cage from side forces. And lastly I would probably add a bar across the a-pillar (across the dash)...