I have considered raw-based formats with minimal headers, similar in some ways to PCX, but I want to explore alternatives that remain practical for long-term maintenance and extensibility.
What are the most important considerations you take into account when designing a custom data format for embedded systems that will likely need to be maintained and extended over the next 10–15 years? Specifically, I am interested in trade-offs between simplicity, memory efficiency, and potential future flexibility. Any experiences, lessons learned, or patterns to avoid would be very valuable.