I would suggest that you have the training base covered on your current plan. However, getting to success quickly requires all you suggest and more. With today's regulatory environment, you will need to look at the firm differently and help your current advisors move up market while creating space for the new advisors at the same time.
Rather than have them work jointly, I have actually moved up my client minimums and allowed new advisors to work with the clients below my minimum. If the clients are properly informed, this should be expected. This creates an added level of service for those smaller clients while giving the new adviser time to learn the business. For the seasoned advisor, it forces them to move up their client marketing and frees up the time needed to do it. It becomes a win-win.