With the removal of ext_dispatch_call and ext_get_runtime_storage we made it easier to reason about what a contract can do. However, without those APIs there is no way to have a custom interaction with the runtime.

We want allow chain authors to be able to augment the seal API with additional functions that provide functionality that goes beyond what is provided by the core API. This allows them to tailor seal to their use case.

This customization should be possible without modifying the seal pallet. Those additional APIs should be defined in the same way as other customization applied by the runtime.