AbleCommerce Shopping Cart Software

I was wondering how hard it would be to modify the handling fee on UPS to be based off of the total sale, If you build your own shipping method it allows you to do rates based on a fixed amount or percentage and have multiple rows. This would be nice for handling fee's as well.

Anyone think a handling fee like this would be good?

Id like to have a % handling fee based off of product total for UPS.