Our deprecation policy says that we will deprecate features for two releases before we finally drop them from the core. However especially on larger refactoring it's often impossible to keep everything while simultaneously changing everything. For these changes, the answer to the question above is important.
Answering that question is hard, though. No one has all the plugins installed and there is no easy way to search through the code of all of them...
The next step is too make it searchable. This is where OpenGrok comes in handy. It's a search engine specialized on searching through code. It has a basic understanding of different programming languages.
Eg. it can differentiate between a string and a symbol. For example, when you are looking for a class named Table, you don't want it to return every string that contains the word Table.
In addition, OpenGrok is super fast. Searching through the over 1000 extensions, takes milliseconds.
My script and a description how to get this running (thanks to docker) is available at github.
This should be enough to get more serious developers up and running. I'll have to investigate what it would take to make this available as a service on DokuWiki.org itself...
Update: it's now available on codesearch.dokuwiki.org