No, we never thought about HTML output. However, there are multiple other export options and we also ship Python scripts that can be used to plot the benchmark results. The script is not very large, so far, but we are happy to add new scripts if the need for one should arise. What kind of diagrams would you like to see?
Also, I have never thought about using criterion.rs. My feeling was that it is suited for benchmarks with thousands of iterations, while we typically only have tens of iterations in hyperfine (as we typically benchmark programs with execution times > 10 ms). Do you have anything specific criterion feature in mind that we could benefit from?