Sorry to respond late, but better late than never.

If you keep on having trouble on this kind of problem, then perhaps it would be valuable to do some post mortems, think about why past projects went wrong rather than trying to come up with idealized plans for how to do better.

It doesn't matter how good the design that you come up with is if you can't get people to buy into it. Or if people say that they buy into it and then erode the design. Or if you erode the design and only afterwards realize that you have done so.

At Re (tilly) 6: Code Critique I pointed out some of the factors which come into play and cause our well-laid plans to fall apart. You might read that, think about the past, and see if you can identify how to head off potential problems before they become real ones.