What is the official term (within a (software) project organization) for calling someone who is not a programmer however (s)he plans the nuts and bolts of the system, it goals, challenges and conceptual architecture. (S)He may be called researcher, but I'm looking for a more precise term.
Sounds like you're describing a systems engineer:
Systems engineering integrates all engineering disciplines and specialty groups for a project into an efficient, streamlined process that smoothly takes the project from concept to production to operation, meeting all the business and technical goals of the project. [ASME]
How about the "systems analyst." (Disclaimer: My wife was a programmer-analyst before she retired.)
The role of the systems analyst is to translate the plain-language, non-technical stated goals of the clent into the pseudo-languages used by programmers deeper in the software development team. A systems analyst can often create a proof-of-concept to demonstrate and debug the function of the intended program.
To systems engineer and systems analyst I would like to add architect, with any appropriate prefixes and qualifications: systems, software, hardware, but also lead, senior, principal (note that "Principal Engineer" can be a legally qualified and restricted term, I believe it is so in Canada).
I would rank the architect above the engineer and the analyst in importance.