Very interesting, thanks for sharing. My main problem with the design doc would be how to cater for changes (e.g. due to technical reasons) that are found late

Very interesting, thanks for sharing. My main problem with the design doc would be how to cater for changes (e.g. due to technical reasons) that are found later on during the implementation phase: as suggested this would require a complete halt of the process and re-evaluation of the design doc, which doesn't seem feasible in practical terms... Wondering if anyone has done this before.