Exactly! You put that very elegantly. (I call that proposed flag "use sane")
I always thought JS needed static types to fix the insanity until I tried Python and realized that almost all the insane BS I get in JS are all runtime errors in Python.
There's a very good case to be made for reducing runtime errors, but it's a hell of a good start to at least have them!
Rather than what we have now, which is "assume the programmer is a beginner, who also never makes mistakes", and "given nonsensical commands, just do nonsense, and propagate garbage data throughout the entire program".
Achievable by just removing automatic type coercion. Throw errors instead.
Would need to be feature flagged for backwards compatiability.