First question that you should ask is "Why is date not negotiable?" This should provide you the rationale for prioritizing features. Identify the core features

First question that you should ask is "Why is date not negotiable?" This should provide you the rationale for prioritizing features. Identify the core features and push for negotiation on the other set of features. Looks like money is not the problem. In that case be aggressive on your search for 'off the shelf' apps (open source or commercial). Can you buy a working product and develop the addons? Can you buy an application and modify it to meet your requirements? When all that fails then see if you want to develop the app using third party components. Easier said then done but it's better to spend time on questioning the rationale for each high level technical decisions and feature request.