Ethically maintinaing a herd of host mother elephants, raising that many mammoth babies, the success rates for implantation, its not going to be a fast process.

"Mother" nature has one timetable which can't be altered. An elephant pregnancy lasts 18-22 months. And, a herd (assuming its Matriachal like elephants) will need to establish a dominance, and a matriarch. That will be a decade or more down the line: You can't lead a herd as a teenager.

An elephant typically gives birth every 4-5 years. So, you need multiple cycles to establish a family. This process probably needs a lot of sisters and aunties to work, they're complex social societies.

(shared a house with a Botswanian wildlife ranger decades ago, He said nothing about African herd animals is simple)