Probably not.

1. Pro Stans is typically for personality/cockpit climate types of issues and will often not even touch safety issues. Reason being that the union doesn't want or need responsibility/liability for determining if a pilot is safe to fly, nor should they. That is inherently the company's responsibility. Pro Stans might be able to give you some advice.

2. The training dept. and therefore the company is clearly aware of where this guy stands, and hopefully IOE will serve as a backstop if needed.

Getting involved could easily blow up in your face.

If the company is so desperate that they are intentionally pushing dangerous pilots through the process, your only real recourse is probably to contact the FAA. Some companies have anonymous safety reporting systems, but even that might not tell the company something they didn't already know.

I assume you already 121 experience? If not, probably best to let this one play out, observe and learn.