I need a customization of: YITH Dynamic Pricing per Payment Method

General information for the website: Sell school uniforms, books and library arts.
Kind of development: Customization of existing website
Description of requirements/features: If you don't know the plugin you can see it here: https://yithemes.com/themes/plugins/yith-dynamic-pricing-per-payment-method-for-woocommerce/

That plugin suitable perfect for me until last year, but now I need something different that this plugin does not offer me.

This plugins deppends on the payment method decrease, increase, etc, the price amount of the whole order. What I need to do is the following.

Product 1 (Category 1): 10 usd
Product 2 (Category 2): 10 usd
Product 3 (Category 3): 10 usd

All the products of category 3, in this case, should have a 10% of discount in cash, so the sum should be, 29 usd and not, 27 usd as actually would does the plugin. I should be able to add many category poducts of WooCommerce.

It is possible to add the customization in functions.php to avoid problems when upgrade?

My main site is www.tiendadelcolegio.com, I can give admin access if needed.
Extra services needed: Customization
Extra notes: