I don’t think this feature should be implemented at all imo.
I hate it when game engines, namely Unity, have an error message popup when you’ve messed up your code in something.
The script analysis window should be enough for 99% of developers and having a broken script won’t cause your game to crash, unless you have an infinite looping while loop or for loop.
It’s extremely bad UX to force stop a developer from testing their game just because there’s a syntax error.
As for the opt in / opt out feature, I don’t think many developers on Roblox would even consider opting in because of the aforementioned poor UX.