I have discovered something interesting. No one is allowed to change their devil fruits however when this is posted they must stay the same.
When a Devil Fruit user dies, their ability is reborn into another fruit of the same kind. Instead of growing from a plant, the ability simply regenerates inside another existing fruit, as seen when Smiley "died" and the Sara Sara no Mi, Model: Axolotl transplanted itself into a nearby apple. Another characteristic of a Devil Fruit's growth is that the stem becomes noticeably curlier than it was when the fruit was not endowed with the ability. In the anime, it was also shown to change its color.
I found this on the wiki and I thought I would show you guys.