vTiger CRM customisation

We have vTiger 7.1 version and we would like to add new features to it. In VTiger CRM, I would like to have the following features. Customer signing the contract. I want to send contract to client. The contract will have terms and conditions and client needs to accept it and sign it digitally. Once they done then we will record this in our CRM along with Date and time stamp. We will generate the PDF of the contract too which I can save and may send it to client via email. Customer portal: We have some clients who’s projects are running but they need to be involved into project task, resource, time etc. We need to provide a portal to client where they can see their projects and its details. They can also create a task, an issue, comment on task etc. They can upload the document too if required. If multiple projects are running for same client then they can see all the project belongs to them. Calendar: We need to send meeting invites to clients via calendar. Once we create a meeting and invite clients then system will send an email to client for meeting details and ask them to accept it. Once they accept it then we will get notification into our system. I need someone who is very good and professional in it and looking for ongoing long term relationship.