(I feel this is a topic for a meta question. I hope You agree.)
A common type of WB question is the "Could device X be built in time/culture Y" reality checks.
While those questions are certainly valid, the answers generally focus on the supporting tech level and infrastructure of the era.
Q: Could my time traveller build an assault rifle in medieval times? A: No, metallurgy and manufacturing were not up to the task, and you could not get working ammo back then.
Well, if the time traveller had knowledge and resources enough he could "invent" modern metallurgy, blast caps and manufacturing methods. It certainly would not be belieaveble, but not technically impossible.
So, shouldn't we either:
- Recommend that such questions are rephrased as "What are the major obstacles if I want to build X in time/culture Y?" (Which would make the answers more clear)
- Define some canon "feasability levels" ie
- Protagonist can build device only given common knowledge from his own time.
- Protagonist can build device given exceptional knowledge from his own time.
- Protagonist can build device given above plus lots of time and resources.
- Protagonist might build device given above plus trust and backing from some major authority of the time/culture.
- Protagonist can ony build device given ridiculous handwaving.