I am pretty sure that exchanges of ANY kind are against rules. That being said, at the resorts come of the CM's allow you to exchange some snacks for a CS meal. They should because technically you get an entree, a dessert, and a drink, The dessert and the drink (bottle water or bottle milk, or OJ, etc) are essentially 2 snacks.
So if you want 2 snacks for a CS meal you wont have a problem at most CS places or resorts. If you went to a ice cream wagon or the funnel cake stand and tried to get 3 funnel cakes for a CS meal, I dont think that would fly. In fact I am sure of it. But sitting down for a CS meal, you should be able to (at the least) get 2 snacks.
That is the ONLY exchange you will be able to get away with. With the exception of possibly a CS meal for a TS credit, which in my opinion is ridiculous. There are plenty of TS locations you CAN walk up to without a Ressie and it will be much better than any CS meal.
Here is a thought, try using the Dining Plan the way it was intended, I always make all of my TS reservations in advance and basically have every CS meal at least thought out. Maybe not where we will get a CS meal, but on:
Monday we will do CS for breakfast, midday snack, TS Dinner
Tuesday TS Character Breakfast, snack lunch(muffin croissant at main st bakery), CS Dinner at hotel.
etc....
i find if you plan out your meals, you find that you get the most out of the
DDP and dont end up wasting credits.
When doing a signature meal that takes 2 TS credits we sacrafice a oop meal at Earl of Sandwich, which is good and cheap, and the other meal of the day would be a CS credit.
Granted we are 2 meal a day family and 1 snack also is usually too much for us. Especially the desserts you get with the TS meals, we often take back to our room because we are so full. BUT we drink alot of water and juice and milk, so our snack credits are used up daily.
Try to plan out your meals it will pay off!!!