B2B Payments for WooCommerce

My client is looking for plugin that allows partial payments and we like your plugin but they need a more custom option for admins. Specifically, they need a payment plan that allows admins to add custom dollar amount that is applied to the order total. Your plugin allows predefined dollar amounts, fixed or percentage. However, my client needs the ability for admins to set the payment amount while they are on the phone (or in person) with a customer. Maybe, while creating a payment plan, there would be an additional option after fixed amount and percentage called ‘user defined amount’ or something similar.

Are you able to add this feature? What would you charge for adding this feature? If you need more details or examples for a use case, let me know.