I will briefly list some of these potential selection criteria for your consideration in case you also could be interested in breeding pet budgies as a hobby or commercially.
1. Vitality and robustness and adaptability to a wide range of climates and diets
2. longetivity.. many exhibition budgies have a quality of life expectency of 3-5 yrs, some are even shorter. The oldest budgies I have cared for have been late teens and early twenties so we have an idea of what is possible.
3. free from zoonotic infections especially chlamydia
4. Free from immunosuppressive and cancer inducing viral infections and other infectious diseases (long list)
5. friendly, confident, playful, interactive, curious
6. easy to tame
7. prolonged easy taming period (currently before 10 weeks of age, and in Australia it is illegal to sell birds before they can self feed, so for budgies this is usually around 5.5-6.5 weeks of age. Let’s extend that to 12 to 14 to 16 weeks of age.
8.Good talkers and easy to teach to talk, wanting to interact with people and listen, intelligent
9. Physically robust and free from genetic modifications that interfer with ability to fly, to perch, to see (without obscuring feathers in any direction!), to keep their face clean, to preen, to keep their vent clean.
11. Easy to breed without being chronic egg layers (cf poultry producing eggs for human consumption)