If you can afford to sacrifice that much performance just to run some potentially unsafe code, then you can probably afford to not be writing Rust in the first place and instead use a garbage-collected language.
This is presumably needed at the integration point, i.e. you already have some C/C++ code being integrated into Rust. So "write it in a different language" is not helpful advice, since all of the code in question is already written.
(However, the technique here is itself not sound, per the other threads.)
