If Bethesda had really wanted to do so, could they have made a crash log that would have identified exactly why f4 was crashing,as in "this mod,in this place, at this trigger." Or is that, from a programming perspective,basically impossible?

Nothing that specific and useful would be possible for the same resaon that papyrus logs can't be used as crash logs, the crash happens way before the game can log anything.

The best they could do is something like what NVAC does in FNV, giving you the memory addresses of the exceptions and you'd have to try to use those to figure out where the crash happened in the code. Even then it is super vague, like "this crash is probably model related" and so on, nothing close to "this mod did it here for this resaon".

(Disclaimer, the technical side of this stuff is far beyond me, I'm just using what meagre knowledge I've managed to to pick up from people much smarter then me)