changing eshop plugin for wordpress into e-ticketing system

The eshop plugin for wordpress should be adapted for selling e-tickets. Modification: When visitor pays by paypal, he gets immediatly his tickets (pdf) by mail or can download his tickets. Tickets should mention in barcode a unique id (att: eshop makes only 1 id per order) the productname and option field. When paying by cash/banktransfer, visitor recieves an invoice. Admin section: when changing the order status to shiped the buyer gets an e-mail with the tickets or a message where he can download the tickets. Admin has the possibility to send reminders to clients who did not pay yet. Admin can print e-tickets per client. admin can add tickets from backoffice and print ticket immedatly. Download section, possibilty to download a file for controlling the e-tickets at the entrance. Option: admin can select normal ticketing or e-ticketing.