Build a magento plugin

I need a magento plugin that gives users the capability or fully customizing a product. The product itself will be products already on the store. This plugin will only be activated for products that it is activated on, NOT all products. The customization must be a drag and drop. User will be able to drag and drop items into certain area on the object. User will be able to change color of certain parts of the object. The user will also be able to add text to only a specific area of the item. Each item the user drags and drops onto the object costs money and must calculate. The user will be dragging "options" that are already in magento for that object. 1 item, $.50, if they drag two, $1.00 etc. If user writes on object, it is free up until 10 characters. If they enter more characters there is a charge. The areas for adding text and dragging items is different. Current existing "tshirt" designer plugins do not work for this reason. We need "text area" and "item decoration area." two separate and sometimes overlapping areas on the object the user can customize. Again, whatever the user drags onto the object, has a cost associated with it. User can also change colors of certain parts of the object, which have costs as well. Please give your full cost on the b uilding of this.