Well, I always have the problems like this in my activity (I develop GIS systems on SQL databases). But the problem isn't me or the technical staff. This problem must go to sales, because sales want more and more lines in reports, more layers (from complex analyses) in map windows that the client really needs, and sales insisted that the client must use that unnecessary garbage, because ,,it looks great and shows a big amount of work". So for the start all looks great and shiny (but from my point of view unnecessary complicated) and in time, when client puts more data in system, all will go down, including the interface (which became too hard to understand). So begins the ugly work of redesign interfaces and explain to the customer that the initial approach was simply wrong...

Designing a good/working interface is as important and difficult as designing a good database structure...