It's not hard anyway. You can just upgrade server frameworks to render the stack trace to either a string or a json data structure (or protobuf), and when an exception bubbles up you capture it, convert it to that structure, compress it, possibly encrypt it with a shared key (just to avoid leaks in case there isn't a proxy stripping the special header), base64 encode it and stick it into a special header. Then your HTTP client can be taught to look for that header in case of a 500, decode it, turn it back into an exception and rethrow it.

If you have a unified framework like Micronaut it's probably the work of an afternoon to throw together. The hard part is the crypto. The moment you introduce keys, corporate security teams will insist on things like frequent rotation even if it's just a backstop against badly configured frontend servers and not mission critical (if you leak a stack trace, ok, not great but not the end of the world). So it might be better to obfuscate in a different way that isn't meant to be fully secure, or detect if a request comes from an internal IP in a secure way, etc.