The main problem I have with this approach is that I believe it will take 2+ years just to get any new team to really get used to each other. If you go young that works. If you start pulling in 29-year-olds then by the time you are ready to challenge, they are on the downhill side and your window is very short.
Having said that, Horford might be able to come in and kick start things while you wait for Leonard or someone else to develop. But, you better plan on trading away Davis and/or Plumlee because if Horford is on the team, then you can probably only develop one other big besides Leonard. And, if Harkless doesn't step up big time, you better look for a solution at the SF position, because I'm not convinced Aminu is the answer.