True, it's very tough to address all of the issues that the aging design of the 5mt transmission presents... There was some company offering a steel collar and over-sized throwout bearing at one time, not sure if they're still in business. I figure adding some strength can't hurt. That's sort of the idea behind testing the case itself. This way I can zero in on specific areas that need the reinforcement most even if I can't solve all of the 5mt's design woes.
The aluminum shift bushings would be fairly low volume production meant for competitive driving. They'd definitely transfer some gear noise into the cabin. However, race cars tend to be noisy and unforgiving. I wouldn't recommend that kind of thing for somebody that doesn't want a noisy daily driver... unless you're a weirdo like me who loves gear noise.