I have had a quick look at the code and came to pretty much the same conclusions as @outsidecontext.
I don’t think that it would be too difficult to make this plugin work in Picard v2, and then not too different to look in the metadata for the recording date rather than the earliest release date for the recording.
That said, I am not sure just how consistent the MusicBrainz metadata is for recording date. Supposing you had a copy of this CD of Let it Be by The Beatles and we look at the track 6 Let It Be. (I picked the Beatles because their recording dates are pretty well documented, and Let-It-Be because of the multitude of recordings available.)
Let It Be
engineer: Glyn Johns and Phil McDonald (engineer and producer)
producer: George Martin and Phil Spector
drums (drum set): Ringo Starr (The Beatles) (on 1969-01-31, on 1970-01-04)
electric bass guitar and maracas: Paul McCartney (The Beatles) (on 1970-01-04)
electric guitar: George Harrison (The Beatles) (on 1970-01-04)
guest Hammond organ and Rhodes piano: Billy Preston (on 1969-01-31)
piano: Paul McCartney (The Beatles) (on 1969-01-31, on 1970-01-04)
background vocals: George Harrison (The Beatles) (on 1969-01-31, on 1970-01-04), John Lennon (The Beatles) (on 1969-01-31), Linda McCartney (on 1970-01-04) and Paul McCartney (The Beatles) (on 1970-01-04)
lead vocals: Paul McCartney (The Beatles) (on 1969-01-31)
recorded at: Apple Studios in London, England, United Kingdom (on 1969-01-31) and Abbey Road Studios: Studio 2 in St John's Wood, Westminster, London, England, United Kingdom (on 1970-01-04)
recording of: Let It Be (from 1969-01-31 until 1970-01-04)
As you can see, for this well documented recording there are a multitude of dates shown - and in this case they are reasonably consistent. But for other recordings of other songs by other artists, the data might be inconsistent or far more sparse. So the difficulty will be in coming up with an algorithm that will identify all the possible dates in the metadata that could indicate the recording date, and then make a decision about what date to use as THE (one and only) recording date - ideally eliminating any metadata which appears to be way out of line with the majority of other dates.