Modify WP E-Signature plugin

i'm building something like freelancer.com. So is a portal between freelancer and employer. i want to use wp-signature plugin to create a contract between the users. Now the plugin can create a contract between 2 users but you must insert manualy the email of employer and freelancer and invite them to assign… So, I would like that in automatic, when a freelancer want to apply a proposal, he has to insert his Offer and the delivery days. The actual details become the contract that must be compilate with only the personal information (name address...) and sign from freelancer to apply the project. The contract is composing from info of employer, info of freelancer that are the only fields that are editable… In the contract will automatic add the skills that employer selected when post a project… So, in automatic the contract will be generated with object of contract that paste the skills with their description. The name of the project employer selected will add in the contract too. The contract has a part dedicated of price more vat. This is not editable from freelancer because he must insert is quote in the box of offert… and in automatic the contract will read that field and repeat in the part of the contract dedicated to the price. The same thing happens to the date of delivery… So when freelancer will compile the fields and sign the contract, the employer recive the proposal, with the contract… with all fields compiled except info of freelancer and his sign. This because employer should not know the information of the freelancer to contact him outside the Sitemeup. So employer will receive a contract without knowing the identity of the freelancer but being able to read all the conditions and services provided for that price and when it will be supplied. Employer to view the freelancer information, compile his fields and sign the contract, must pay before, Exactly like do the site now when employer accept a proposal and ask to transfer founds. When employer has paid, will compile his fields and sign the contract. The freelancer will recive the contract assign from employer with all the information.