Separate the contract from the implementation.
An open interface is a clear technical contract: data format, timing, electrical behavior and failure handling are understood by both sides. The implementation behind that boundary can then evolve while the wider platform remains stable.
Integration is a lifecycle concern.
Connector selection and protocol support are only the beginning. Versioning, diagnostics, synchronization, configuration control and backward compatibility determine whether an interface remains useful through upgrades and changing mission needs.
Modularity still requires ownership.
Modular systems do not remove systems engineering. They make it more important. Someone must understand the end-to-end behavior, define boundaries and verify that the assembled system performs as one coherent capability.