Should this be in the wrong sub-forum, please let me know where I should be posting or, if you're a mod, feel free to move the topic (but let me know where it went!).
I'm consulting on a Magento webstore and right now there is a huge problem with shipping and stock. There are a ton of products on the store but not a whole lot are actually in stock, local or otherwise. There are also a few products that are made to specification / order. The suppliers have a number of different ways to ship, either by specialized courier services, or national post.
We've debated waiving the shipping costs altogether after a certain amount but that honestly only works for products that they actually have in stock. For a long time they used a 3 dimensional table rate system where every supplier / manufacturer had their own set of shipping rules and costs but that has been cumbersome and troublesome as well. Keeping shipping costs up to date was one issue, shipping costs varying from time to time another. Another problem was that all those products were listed as "In Stock", even though the products weren't physically in stock at the webstores' location. Sometimes it would even go as far as the product not being in stock at the supplier or, even worse, the product had been silently discontinued.
Right now I'm looking for a way to make things a little easier, or at least more intuitive. I'd need a way to get one more stock status, ie. "In stock at supplier", "Special Order Item" or something along those lines. Once a product with that status is being added to the cart, it should be impossible to actually get a shipping quote or pay for the order. One of the store's employees would then have to step in, check if the product can be ordered, how much shipping to the customer would actually cost and then add that amount to the order and ask the customer to pay.
Now I know this is a little backwards and to be honest I would like to fully automate the system. However, it's impossible to probe every supplier each week or day for an update as to how much stock they have of any of their products. I expect a handful to actually do that the first 3 times, but after a while even those will get fed up with that.
If anyone has a solution to this problem, either in the way of a plugin / addon / modification or a different view on operation methods, please let me know. These people are looking at me for advice where I'm actually running out of ideas myself. I haven't found any plugins on Magento Connect that might do what they want and the few that might scratch the surface are too expensive to take a gamble on.
This magento extension can help you with your requirement:
You can also check out this extension https://www.magentocommerce.com/magento-connect/custom-stock-status-by-amasty.html
It will help to inform customers about specific stock statuses. However, it won't disable payment option once one of such particular products is added to cart.