What's your idea?
Allow flagging of modules, at least "favorite" modules, possibly also "to review" modules.
What are the benefits?
Allow users a way to keep a sensible and authoritative list of modules they like, for later referencing.
What are the risks?
If the number of flags on a module are exposed to the public, it risks marginalizing new modules. This can be avoided by not making this a publicly visible metric. However, it's worth noting that this risk is already present as a result of showing the "number of downloads" and "usage" on module pages.
How can we measure the impact of this idea? (metrics)
By literal usage. How many modules are flagged? By how many users?
Who directly benefits from / will use this improvement? (target audiences)
Site builders, developers.
Are additional resources available for discovery/implementation? (volunteer effort, financial backing, etc.)
Not that I'm aware of.