All that remains is to collect the unique stories of the people who have been behind the development of cryptocurrencies almost from the beginning
You are looking for a very select group of individuals to contribute to your book. And I really don't know if early developers would be interested in reporting their story to you, because it's seem likely they would prefer to write a book themselves.
If you have friends who are major bitcoin hodlers (bitcoin only),i will listen to their stories as well
What do you mean by major bitcoin holders? What is the minimum number of btcs someone must hold to be considered a major holder for your research?