Ability to set up payment schedule for subscriptions

We would love to have an ability to set up uneven charges with a specific customizable date of next payment. Example:

1st payment: 18000 MXN
2nd payment: 3500 MXN, +26 days
3rd payment: 3500 MXN, next month
4th payment: 3500 MXN, next month

Currently we have to use product + plan mix to be able to provide such option