I agree with you about Tracy's mental fortitude Iain but the Evert-Navratilova obstacle I had in mind was more along the lines of having to play well enough in two successive matches to beat both to win a major.
That worked the other way round too. Martina beat Chris but failed to beat Tracy at the US Open in 1981. Tracy DID beat both Chris and Martina to win the 1979 US Open. When she did it again at the Toyota Chmps she became the last person to do this until Mandlikova in 1985.
I think Evert never had to beat Tracy and Martina to win a slam.
Martina defeated Austin and then Evert to win Wimbledon in 1979.
Anyhow, I realize you were projecting this foward into the mid 80's, but assuming Austin was healthy we really don't know how Austin could have responded.
(a) a vast physical improvement in Tracy's game (b) a notable development in her tactics (c) a real beefing up of her serve and (d) efface the psychological damage (e.g. 06 06) done in 82/3 during her 'declin
a) If Martina and Chris did this with older bodies, why not a younger Austin?
b) She was pretty smart cookie. At the Open in 1981 she suddenly hit to
Martina's forehand out of nowhere.
c) Her serve improved during her comeback in 1981. I doubt if her serve
would ever be great, but then neither was Evert's
d) She overcame some psychological baggage in returning in 1981. Again,
if Evert could face the monster in mirror (Tracy) and Martina could get it
together after her 1980 meltdown at middle-age.
Anyhow, that's me playing devil's advocate for the day.