What is the problem you are trying to solve?
Order Rules are superior to Order Validators in almost every single aspect (enabled through the UI, configurable through the UI, support eligibility framework, etc.), except the Order Rule is only triggered when starting the checkout process while Order Validators are triggered whenever there is an item added to the cart. I have a use case where I want the configurability of order rules and I want to use the eligibility framework to target the rules to specific order types or accounts but I need the validation to occur when items are added to the cart.
What is your project about? (e. g. Intranet, Partner Portal, Enterprise Website, etc)
Customer Portal with Commerce Capabilities.
What is your proposed solution? (optional)
Create a new method in the Order Rule interface that would be called when items are added to the cart, similar to what we have in the CommerceOrderValidator.