May I remind you that both the U-2 and SR-71 were developed in a very tight, totally classified, project team environment with very little gubmint meddling and highly expedited approvals of all changes. Even so, no two birds of either type were of the exact same configuration, and there was no production run of either one. That is more akin to satellite development nowadays except for the gubmint meddling and gross funding instability...
JC
Be that as it may, it still shows that is was possible to do bleeding-edge flight platform developments on-time, on-budget... as long as you keep a tight focus on your goals.
Bring in more than one branch of the services, and you’ve complicated your problems tremendously. We know this from multiple projects in the US military inventory.
Bring in more than the US services? Absolute insanity is the result.