A lot of these ideas are closed as "plugin territory". However, saying a problem is solved by "numerous plugins" doesn't really help -- especially a few months later when some of the plugins the admin was thinking of are no longer supported.
I know this whole problem is 1000% times harder than herding cats, but it'd be wonderful if something like the following happened:
1. Somehow, somewhere create a table that links ideas to plugins.
(i.e. so someone who finds an idea that matches a problem they are trying to solve can find links to relevant plugins)
2. Create a similar table for "pluggable" ideas for which no current, up to date plugin exists.
These could be ideas that are just one offs that haven't been coded yet.
Allow people to vote for these ideas and provide a "most requested" plugin list that might guide developers.
3. When an idea is marked as "pluggable", the admin making that decision can either -
a. Know of specific, up to date plugins that apply -- add those to the list in #1 related to this idea
b. Just "know" that the idea is a reasonable area for a plugin developer to tackle - and add it to the list in #2
4. Have some sort of automated system that goes through the plugins in list 1 and moves the related ideas to list 2 when the plugins in question no longer support the current version of WP. Alternatively (or in addition), copy the ideas to the list in #2 in a specially marked category ("there may be a solution - check list 1") when the plugin was last updated long enough ago that WP has undergone some number of upgrades. This would flag plugins that may have been orphaned.
5. When a plugin is submitted to the repository, include a way for the author to mark which ideas it addresses and update list #1.
I'm sure there are many difficulties that I'm glossing over -- but my experience in trying to find current plugins for relatively simple (and eminently pluggable) features has been frustrating so I'm dreaming big.
Thanks all, for the core, the plugins, the themes and the whole ecosystem.
[Another related idea can be found here: