Restrict purchase quantity by category and separate or list products by category on invoice

[ChrisRabkin]

Hello,

I am looking for a solution that will allow me to restrict the quantity of any 1 item or sum of items by category. I need to be able to set a limit because some products are 1 of a kind and my need is to allow or disallow someone to buy all or only a few products based on category.

I also need a method to group products from the same category on invoices/orders in the back office. 

I am having difficulty finding modules that will work with this- sometimes it's just because Im not asking the right questions.