PHP, Ajax, Community Script

We are currently in search of a community script that actually works. We have tried several of the canned packages such as Dolphin, ABK, E-Meeting etc and have found them to have numerous bugs and problems. We are looking to develop our own script that is similar to the ones mentioned but that actually works. We will be using the script for a specific market and will need most of the functionality that is included in the bad scripts mentioned. We are not using the script for anything adult in nature. We do need several custom pages including a custom page for sales that we will discuss with the developer. All chat rooms, im chat, video chat is to be incorporated into the script without the need of a third party software provider. We would like that all chat mechanisms are written to use the least amount of bandwith possible from the server, preferably ajax based or even cloud based. We need full site design and banner sales creation. We will also need the developer to sign a non disclosure agreement, an agreement for copyright ownership to us and a written guarantee for future support. Upon completion of the script, we become the owner and can do with the script as we please. This is not negotiable. The script is to incorporate most of the functionality that the other scripts that were mentioned have. The script must be easy to install on a web server. The script must have the ability to be upgraded as technologies progress. We will guarantee the developer all future work including site design. We will also grant the developer free banner advertising on the site for a specified period that we will discuss with them. We are open to all suggestions made by the developer. We are also pressed for time and would like something that can be finished in a reasonable amount of time. I actually have a working copy of the ABK script that we purchased that can be used for reference. The script is bug filled and virtually useless but it has alot of the modules we are looking for.