All IV's need are a set list of priorities to follow when passing down from parents, so that a good breeder can map out a route to the exact IV spread they want.
1) The game checks if a Power Item is being held, and passes down that IV. 2) The game then checks for up to three IV's of 31 from both parents, and passes those down (chosen at random if more than three to choose from). 3) The game then checks for the highest IV remaining from both parents, and passes that down. (Chosen at random if multiple IV's tie) 4) The game then checks for the lowest IV remaining from both parents, and passes that down. (Chosen at random if multiple IV's tie) 5) If all of the previous steps are done and the offspring is still missing IV's, THEN the game will randomize the remaining ones.
With this system, breeding is much less about rolling dice, and more about planning; rewarding the player for utilizing the tools available to them. It would only take a couple of generations of eggs to get your desired results if you know what you're doing.