To remove the whole section (for a Targa effect) would probably require a windshield change - the T-top would be easier to do and require less modification due to stress from an unsupported windshield. The removable rear shouldn't be difficult, however you would have to deal with the rear tire hump or change the tailgate completely.

I'd love to see a real working convertible - if you can overcome the design obstacle I'd say GO FOR IT!

-- Best, John