I am happy to learn that you can buy5-6 foot trees that have already been grafted. Haven't found any for sale that have 40 varieties of fruit. But you can get a few different ones. Harder for me since I have to be carful about my zone. But I really like this idea. Having just a few trees to get so much different fruit is much easier to care for and clean up the yard.
Not sure about the trees resilience to disease and insects though.