This is a great idea, and I'd love to participate. For reference, I'm a PhD student at Stanford working on the intersection of programming languages and cognitive science. It's my goal to understand how programmers learn and use programming languages, especially ones like Rust.
First, it would be good to collect prior work into Rust's learnability. I've worked on this a fair bit myself:
- I made a curriculum that teaches Rust as a part of Stanford's course on programming languages: http://cs242.stanford.edu/f19/
- I analyzed dozens of blog posts from new Rust users to identify barriers to adoption: https://arxiv.org/abs/1901.01001
- I wrote about how incompleteness makes it hard to understand Rust's ownership: https://arxiv.org/abs/2011.06171
- I identified ways to improve Rust's generated documentation: https://arxiv.org/abs/2011.05600
Second, we should think critically about methodologies for identifying learning barriers. I know surveys are the default method for the Rust community. But there are more effective methodologies for generating useful insight into issues of HCI and pedagogy (see Table 1 of this paper for a good list).
For example, user studies. A few weeks ago, I ran a user study where I asked a few Rustaceans who didn't know warp (marketed as "super-easy") to make a 10-LOC change to one of the examples. I saw even veteran Rust users struggle to find relevant examples and make use of documentation. Inspired by that user study, we developed a rustdoc extension to link examples within documentation that we're looking to merge soon. I honestly don't believe anyone would write on a survey "I wish rustdoc linked to the examples/ directory", but that kind of insight is often more apparent by careful observation of users at work.
The point is: how you study learnability is quite important. And as a project group, we have the opportunity to create infrastructure to facilitate methods of inquiry. For example, imagine if we maintained a mailing list of people willing to participate in user studies. This would make it easier to quickly find participants, which is often a big non-starter unless you have an existing network of Rustaceans.