Incoming Partner Link and Personalization

I am very new to WordPress. I’ve spent a good week searching for a plugin solution to my problem with no luck. I am running the latest 3.6.1 multi-site, and I have a dozen or so sites setup as sub-domains.

Brace yourself, it’s a long one…

When someone hits a partner link (i.e. – ‘?partner=friend1’, ‘?partner=friend2’, etc.) on one of those sub sites, I need that sub site to have personalized variables for images, partner name, phone, email, etc., preferably in the form of short-codes. If there is no partner information, I just load default values.

In other words, if the visitor arrives on the site via a partner link, our partners basically own that site for the duration of the session, and hopefully the cookie’s life. This should be as hidden from the visitor as possible.

My current solution uses mu-plugins functions that accomplishes the following:

1. Read the partner URL variable or existing cookie.
2. Loads the partner information into the current session and cookie.
3. Redirect to the home page without partner information.
4. Displays a personalized version of the site.

My solution works, but I need a more elegant and scalable solution than having an ever growing custom functions file (of partner vars) in mu-plugins.

My ideal plugin:

1. Ability to add a partner profile: name, logo, email, phone, etc.
2. Add a partner url (i.e. – ‘/partner1/’ cloaked) that redirects to a main page of the site, but stores the hit, and changes the personal vars.
3. Have the site personalized with that information for the life of the session/cookie.
4. Statistics would be awesome.

I’ve looked at literally every single affiliate plugin, from free to paid. I don’t think I’ve found any that have the ability to personalize your sites based on incoming links. Every plugin under the sun exists for WordPress, so I figure I’m missing something.

Any help is appreciated… from plugins, to the best place to hand write the code, or even to store the personalized vars.

Thanks,
T