I like this question, because you are not asking for a solution, but 'a way to think about it' which will help you and your clients make good decisions.
@JeromeR's recommendations are a great way to start thinking about a homepage, convincing others to think in the same way, and setting a vision for your application.
As experienced designers and realists, we know that we won't get it all right the first time
Just as important as the initial design, is to set up an environment for continuous improvement
- Ensure you have analytics and data monitoring build in from the start. Set this up at planning stage and if necessary, reduce features in order to get this into scope
- Think about the type of user behaviour that you want to monitor, and theorise about the problems you expect to find. Ensure your analytics are optimised to report on this in a meaningful way
- Get management buy in and budget early, for a continuous improvement programme. Make sure that there are long term processes, planning and resources in place to make this work
The decisions you make on what goes in will get your product out to market. The decisions you make afterward will ensure it is the best product on the market.