(1), (2) and (3) needs to be one once per lifetime. Or even less, if it was published on cargo.io. It is not an issue. And it doesn't seem as over-engineering for me, it would be like 10 lines of library code, with clear purpose. If it was 50 lines of code, with several methods for different cases, and with a lot of corner-cases, then it might be called over-engineering. But 10 lines of straight self-describing code with two line comment about suggested uses is not.
As to derive for each type, I already use `#[derive(Debug)]` for most of my types, to be able to print them with {:?} in format/println!. Though you are right in the sense, that it would be great to make such a method a part of Debug trait. But I personally have never needed it, so maybe complications of Debug trait would be the over-engineering you speak about.
From other hand I do not like variables. Variables are complications of code, and complications like this make it impossible to grasp code on the first sight. There are a lot of cases when you need a variable, and it is not apparent on the first sight which case is it. You need to stop and think. I do not like to think just to find that there was no reason to think. Intelligence is a constrained resource, you need to use it wisely.