One of the bases for security is the age of a program. All other things being equal, the implementation that has been around the longest is expected to have fewer issues than the shiny, new thing (because the old program is well-understood, has been patched to death, considers a thousand corner cases, ran on more hardware, more time passed without any issues, etc.).

As such, changing away from well-known compilers and language behaviors may not be the wisest thing for security.

On the other hand, extending existing compilers to restrict behavior seems reasonable. Also, by all means document the hell out of the things that are not well-defined.