Just a comment regarding this:

There are still some practical concerns with both. Namely, what happens when there is a conflict between supported versions? The current proposals leave it up to the plugins to not break anything on the user’s end.

To provide some context:
Checking for a minimum version is simple enough, and it was initially part of the implementation. However, checking for a maximum version was deemed bad practice because in WordPress all plugins should ALWAYS be kept up to date. Introducing a version-check in dependencies was therefore deemed unnecessary as it would promote bad practices, and the implementation was removed.

Can you imagine for example plugin A requiring plugin B v2.0.x, and not letting users update to v2.1.x? It would be a nightmare scenario for security!

With the above in mind, it was simpler and more efficient to let plugin developers handle their own backward-compatibility, and not force any sites to use older versions of plugins because of dependencies that someone forgot to update on their plugin :)