Custom Cart functionality with sessions

I am trying to create a session based shopping cart system, and was wondering if there was a best way to do this? Currently I have a plan of attack - however some advise on moving forward would be appreciated!

The website has 2 areas, I will call them A and B. A and B are Collections, and each collection Item is a product. What I want to do is auto create the session straight away as a blank object, so that I can push into this as I go along and let my cart session handler work out everything it needs to - this way my add to cart is a simple click and send,

I have looked through the source code for both Shop options available currently in the Add-On Apps, however neither FoxyCart or Paypal are what I am after.

Should I create an App for this? A point to note is that I am also planning on adding in vouchers and discounts into this simple session based cart system.