I didn't get to read your post, but got the gist of it. My ds1 just gave his up for his 4th birthday totally of his own accord. We talked to him about it for a year or so in the end!
Ds2 will be 3 in November and isnt ready to give his up. They only have it for naps and bedtime (but I instilled this from the start so no idea how you'd go about it now?)
I don't think there's a problem with a toddler having a dummy at all. Ds1 hasnt even asked for his since he gave them away (for the babies at hospital, he posted them). He was ready.