We use FoxyCart purely for the payment functionality for a single product, and we don't need the Cart itself really (although the cart page is nice way to display the product details and price breakdown). We merely have one "Buy now" hyperlink which goes to FoxyCart with the product details in the query string. As such, we don't provide our website visitors with any way of adding extra products to the cart, and indeed they don't even know that they have a cart, really! So, we use the empty=true parameter in the hyperlink, since otherwise the visitor would be able to add extra units of the product to the cart if they jumped between the cart and the shop repeatedly. (Actually, I'm not sure if that's true any more, given that we now use the quantity_max=1 parameter [which we introduced to prevent the visitor from manually increasing the quantity once in the Cart page]; but it certainly used to be true before we started using that parameter.)
Anyway, we'd also like to stop the visitor from being able to remove the product from the Cart, since that functionality adds no value in our situation because it results in a useless empty cart and in any case the visitor can already easily return to our shop without going further with the purchase simply by clicking the "Continue shopping" button in the Cart (which we've renamed to something like "Cancel / Back"). I tried using the quantity_min=1 parameter hoping that it would prevent the visitor from being able to manually reduce the quantity to 0 in the Cart (which unfortunately failed - which seems like a bug to me, though admittedly the documentation for it does seem to imply that it only has an effect with the product is a "child product" [which ours isn't, of course] - although it did have an influence on the tooltip which is displayed when hovering over the quantity box), and hoping that it would prevent the "Remove item" link from being displayed under the product in the Cart (which unfortunately it didn't).
So my feature request is: please provide an easy way to prevent the "Remove item" link from being displayed under the product in the Cart (perhaps limiting it to working only when empty=true is used, since I can't see any use case for it when empty=false). This could perhaps be achieved via a new query string parameter (which should have the side-effect of overriding a zero or missing value of quantity_min with the value '1'); or perhaps it could happen automatically whenever empty=true,quantity_min=1,quantity_max=1 are used in combination and only one product is specified.
I guess the workaround will be to edit the Cart template and remove the HTML corresponding to the "Remove item" link... but that's a bit of a hassle!