Custom Plugin For WordPress Multisite: Per Site Registration

I need a custom built plugin for wordpress multisite. These are the HARD requirements for the plugin. No exceptions to these requests. - Must be network enabled, but no settings are given to regular users. Only the Super Admin can see plugin settings. - Must be compatible with wordpress multisite 3.6. - Must be compatible with w3 total cache. - Code must be secure and follow best security AND coding standards for wordpress 3.6 - Must be able to scale with a growing site. - Must be upgrade proof. If I upgrade wordpress from 3.6 to 3.6.1 then to 3.6.2 and even 3.7 it must not cause problems with the core install of wordpress or the database - No hacking core wordpress files. - Must uninstall clean. Meaning remove any unused and created database and filesystem code when it's removed. Description of what the plugin MUST do: The plugin, when enabled, will make the registration link of a sub blog (i.e [login to view URL]) to act and behave exactly like a single wordpress installation in regards to user registration. Meaning, when you click the registration link in the sub blog, it will send you to a registration page on that sub blog instead of the multisite root website. Currently in a multiste site installation, if I have [login to view URL] and someone signs up at [login to view URL] they can create a blog. This is good and exactly how I want it to function. However, if that user makes [login to view URL] and another user visits [login to view URL] and clicks register, they will be sent to [login to view URL] to register instead. I don't want that. I need this plugin to allow multisite blog registration to act as if they are independant websites. This MUST be automatic. Meaning that no intervention is required from me such as theme editing or styling to get sub blog registration to work.