I’ll order what I want and sometimes that requires a special order. My experience from traveling nearly constantly for the past 15 years is that 10 seconds and a couple of lines makes things go far easier .... and I get what I want.
If you want to allow a predefined menu limit you to specific dishes, then fine. I prefer to ask and see if they are willing to make small changes to my satisfaction.
Just because a restaurant will accommodate a special request doesn't mean they like doing it. I eat lunch and dinner out approximatley six to eight times a week. I have owned restaurants in the past; my first job at age 13 was a dishwasher/bus boy in a diner (I later became a short order cook); and I put myself through college and grad school working in the food service industry. Next to customers who snap their fingers to get attention, our number one per peeve was special orders. We would try to accomodate, but we didn't like doing it. And more often than not, we found that special order customers did this all the time at every place they ate, not because of special dietary needs, but to show their dinner companions how important they are. In my experience, 99% of special orders were an exercise of ego and control.
Although the customer may not see the special order as a big deal, I can guarantee you that they are a big deal to the kitchen staff, paricularly during prime dining hours. A good kitchen runs like a well oiled machine, and if a line cook has to spend three minutes plucking the peppers from sausage and peppers, that means that someone else's food is three minutes late or that another line cook has to do two jobs instead of one, which can compromise the quality of another diner's food.
Here's an example: I used to have an ownership interest in a small bistro (24 seats). A guy and his wife came in at 8:00 pm on a Saturday night. He orders the shrimp and pasta, but asks us to cook the pasta without using salt because he has high blood pressure. We have six, stovetop, gas burners, one of which is dedicated to a pot of salted, boiling water, which is primarily used to cook pasta. To accommodate the special order, the chef either has to take the pot out of service for ten minutes while he boils unsalted water for the special order, or tie up another burner for ten minutes to boil unsalted water. Either way, another customer's dining experience may suffer. The worst part is that special order customers are often flexing their egos and can't wait to complain that the special order "is the worst food that I have ever eaten."
Oh, I bet the waitstaff have often made small changes to your special orders- they just don’t tell you about them.