Allow custom fields to be added to decorated products on as case by case basis.

Currently, custom fields work like a light switch..... on or off.  But often, a popular blank product can be used for many different areas, requiring different decoration.  By making custom fields available to decorated products, this would allow the flexibility to select the relevant custom fields required on a case by case basis.  

I have identified 2 possible ways to achieve this:

- Add the 'custom field tab' to the decorated product list.  When I asked about this, I was informed that it would interfere with the option to add a text option in the design tool, where people can add personalisation, but not add a charge for this.  However, I would argue that they would in fact compliment each other.

- If it is not possible to add 'custom field' to a decorated product, there is a tab below 'custom field' on a blank product called 'decorated products', where it shows you how many decorated products are attached to the blank product.  When you click on the number, it brings up a list of all the decorated products.  By linking the custom fields to this page, it would be possible to select which custom fields are on for each design.

Currently, the only work around I can come up with is to create multiple blank products, to cover all possible variations of decoration a product might need, creating a lot more work, and being much less efficient.