It is not difficult to output parsed query in some tool readable format but it comes with a maintain overhead: once tools rely on it, we have to conform to some schema continuously, like the xml/xmlns. Do we want to take this? Depends on how far the tools can go with this exposed information.
We actually already have explain command in json format and tools drawing/analyzing query plan rely on it. Will that work for your scenario?
Sure, that would work - but as I understand adding an explicit SQL command (or function) is not something that would ever be merged into Postgres core. Especially since that command's output could easily change across versions.
My thought was more along the lines of making something like raw_parser + nodeToString available through an extension, but with a JSON output format.
Note that an important detail in the monitoring case is that you don't necessarily have the statement's underlying relations available (since you might work with statistics data on a different machine).