This knowledge regarding feasible developments is of first-rank importance to policy development, yet is commonly ignored.

The problem, of course, is that "this knowledge" may be real, but it has not proven to be particularly practical. There have been many attempts at the process you outline and some have even produced reasonably accurate predictions in terms of particular designs.

Where they failed miserably was in accurate predictions of the timing (the difficulty of producing said design). This is the area that needs most work to improve it's status as a policy tool.