The bi draw for ATL to do the trade is that it would be a way to get Howard to agree to sign there. I'm speculating that Howard wants to play with his buddy Smith, who wants to play with his buddy Rondo (all total speculation on my part). So the trade is actually Horford and Teague for Rondo and signing Howard with their cap room. Atlanta does that trade eight days a week.
I guess an alternative would be to not trade Horford and Teague, and to take a chance on Bynum with your cap space, letting Smith walk, or moving him for a scoring wing in a S and T. IMO that isn't a team that will beat Miami.
Miami is vulnerable to strong athletic bigs and PGs who can create offense against extreme defensive pressure. A Big 3 of Smith, Rondo, and Howard, surrounded by sharpshooting wings, would be the type of team that could give Miami a run for their money.
I have a feeling that Howard wants no part of being the man in LA. Houston or ATL are the expected landing spots for him if he wants out of LA, unless Howard's threat to leave without compensation would force the Lakers tom move him to Brooklyn for Brook Lopez.