Damage Waiver - percentage of rental item

In our industry it is common place to offer a "Damage Waiver" which is charged as a percentage of the rental cost. This is like an insurance against the customer having to pay an expensive repair bill should they damage the hired in equipment. I would like to offer this option through the Rentle platform and was wondering if it would be something you would consider adding? It would basically be aan optional item that you could add to an order that would charge a percentage of the rental charge on top. I can see how i could add it as an accessory item with a fixed sales price but not as a percentage.