Funny you say that- that isn't far from how it was made. Someone wrote a spec script about a human war with space bugs, independent of starship troopers. When one of the production people read the script they brought up the point that there was a book that they remembered that was kind of like it. When they checked, no one had the film rights to it so they bought it for cheap. They then did a quick rewrite to slap in the character names and basic/cheap/easy things from the book to make more of an appeal to the book fans. Then when the director came on board he was a fan if the book but also wanted to do his own thing. So you now had at least 3 different directions the story was going and it was simply held together by the loose premise of starship troopers.