A player can possibly become a dragon with some shenanigans
They will need to be a wizard with the spells clone, simulacrum(more for ethical reasons does not need if morally questionable), magic jar & true polymorph
1. cast simulacrum or get volunteer that has high CR or level
2.True polymorph them into dragon that can shape shift into human like an adult gold dragon
3. have them shapeshift into a human form
4. use brain jar to possess the body
5.clone the dragon body in human form
6. die
7. have you soul enter clone and now you are a dragon with any class abilities still available
I know this is not what you were wanting but maybe this process was what the wish did was share with them the knowledge how to become a dragon this way as it will not be until 17th level as it require 9th level spells
Another option was to just make whenever polymorph was cast on him, he can also become a dragon instead of only beasts as that is the way you could read the wish.
A player can possibly become a dragon with some shenanigans
They will need to be a wizard with the spells clone, simulacrum(more for ethical reasons does not need if morally questionable), magic jar & true polymorph
1. cast simulacrum or get volunteer that has high CR or level
2.True polymorph them into dragon that can shape shift into human like an adult gold dragon
3. have them shapeshift into a human form
4. use brain jar to possess the body
5.clone the dragon body in human form
6. die
7. have you soul enter clone and now you are a dragon with any class abilities still available
I know this is not what you were wanting but maybe this process was what the wish did was share with them the knowledge how to become a dragon this way as it will not be until 17th level as it require 9th level spells
Another option was to just make whenever polymorph was cast on him, he can also become a dragon instead of only beasts as that is the way you could read the wish.