For a high profile demo, the features that should be the highest priorities are the items that provide the most value to the people that are in the audience.
Prioritization using boardroom logic
One way to prioritize a list is to sit in a conference room that has a white board and ask for opinions. List the opinions on sticky notes. Spend hours re-arranging the sticky notes. The problem is that the results will be based on unvalidated opinions (also known as guesses, forecasts, knowledge gleaned from old research reports about potential preferences in the future,... ). It is likely that the loudest voice will have too much influence. The HiPPO (the highest paid person's opinion) will have extra influence.
Prioritization informed by dialogs with customers
A better way to prioritize a list is to interview the potential customers and review the notes from the interviews. To prioritize a list, the team has to 'get out of the building' and learn and confirm what provides the most value.
Not all of the functionality has to be in the demo. Not all the 'important' behavior has to be faked. The more important factors are understanding what the customers value and acknowledging that your team is working to provide this value.
Under such a framework, the team will not have to apologize for features that are not implemented. Customers will be more impressed when your team recognizes that a feature is critical to providing value for them. The customer will be more impressed that your team is continuing the dialog than a slick demo that doesn't match their value requirements.
Demos and new product development
To glean the most value from a demo, it should not be limited to a monolog. Strive for dialog.
A demo provides a unique opportunity for conversation and an environment for learning. The resulting insights can be used to decide how to prioritize the development of features for every new product development (NPD) project.