PHP, SMARTY modifications needed for PIWIGO photo gallery project

Coder needed to modify an installation of PIWIGO photo gallery. PIWIGIO uses PHP and SMARTY to operate it also uses a "Module" system whereby users can add additional functions with the modules. As a photographer I am looking for a platform to use to be able to sell my digital images online. Unfortunately the available alternative software that you can use "out of the box" is inadequate with a lot of missing functions. This is what I would like to be done in my PIWIGIO installation. (This is a basic description of requirements) 1. To have available a choice of image sizes and prices available for immediate download. 2. To have a 'Watermarking system'to protect my images while being viewed. (PIWIGIO doesn't have a watermarking system!) 3. I would like to have the feature of being able to have a 'Multisite' similar to the wordpress multisite function where I can have unlimited sub domains from one installation of PIWIGIO for example: [login to view URL], [login to view URL], 123.domain.com..... 4. To have a PayPal payment function for all images. 5. To have the option of free and paid membership to my site. This is a brief outline of what I would like and would like to hear from anyone experienced to do the work. Of course more precise details will be provided to a potential coder. You can see a demo of PIWIGIO here: <[login to view URL]> or you can visit my experimental installation here: <[login to view URL]> Thank you for reading and hope to hear from any coders.