Even if they don't mind people choosing not to use damage as an option, you will notice that PD have always tried to maintain a level playing field when playing the game. This is the reason why difficulty settings in GT mode have been overlooked, a definite reason why PD chose not to include difficulty, it is not because they forgot, so having a damage option would allow some people to complete the game easier so in effect it has very similar effects to difficulty for these two reasons it won't be optionable in GT Mode.
Actually what makes GT so good is that it does allow each player a great deal of individual control over the "difficulty" level for all the races by allowing in many cases a wide variety of cars, mods, tuning adjustments, and even the ability to change the AI line up of cars for most of the races.
So in effect, while there isn't a simple "difficulty level button" in GT mode, except for Family Races, PD most definitely empowered the players with the ability to have a race in GT mode that will almost gurentee a last place finish, or to absolutely dominate the field, regardless of your skill level.
For example, it's actually very easy to have a near 100% win ratio by selecting cars, mods, set-ups, and/or AI fields that even the most novice of drivers is going to win. While at the same time, it is also possible for a very experienced GT player to have a win ratio under 10% by selecting inferior cars and set-ups against superior AI lineups.
So, no, I would not agree that PD tries to maintain a level playing field, nor should they. If they did, they would make everyone use the same car, same set-up, and same AI field for each race. Fortunately they do not. 👍
A quality game in my opinion should be designed such that the person who plays it can adjust the game settings and environment that best meets their needs at any given time. And even with games like GT4 and F1CE that do offer each gamer a wide variety of game selections to cater to different skill levels and interests, it also still allows for players to compare stats and performance among those using the same settings.
However, I completely agree that modeling complex damage physics for 500+ cars is likely too much to ask. If they can, or do, I'd be willing to bet, like most games today, there will be an option to disable it, and if not, they will likely get slammed by the majority of reviewers and users alike. One thing that today's popular games have made clear, the majority gamers like options, and do not like being forced to play exactly like everyone else.