Given your eloquent summary of the men's game I would be interested in your thoughts on the women's game and Serena's place in history. Clearly there are many who have anointed her the GOAT but without considering many of the details and nuance that you just applied to the discussion of Federer. Feel free to weigh in on that subject if you have the time sometime!
I'll give a quick and dirty for you. I think you have a very small pool of players: Serena, Graf, and Seles. Court got slaughtered by an aging Riggs, which shows the weakness of her era. Althea Gibson is interesting, but her advantage was her physical prowess in a weak era, not sure her skill would be up to par. Billy Jean was good, but more of an icon than a competitor for the title of Goat. Navratilova and Evert deserve a mention as well.
I'll eliminate Evert. She had a lot of success and was one of the best clay court players, but I don't think she could adapt to the physical rigors of the game.
Navratilova is probably the GOAT from a McEnroe perspective: 18 singles, 31 doubles, 10 mixed. Having achieved the #1 ranking in both. She was athletic enough to hang in today's game and could handle power.
Steffi Graf is as good of an athlete as you can find in the women's game. I've heard stories that she could have made the Olympics for Germany as a sprinter. 23 GS singles titles and one doubles GS title. 1988 was one of the best years in the history of the game. She won all 4 GS's and a gold medal. Also the year of her sole doubles GS title.
Seles was a ridiculous talent who amassed 8 GS titles before her stabbing. She only won one more. She may have been a no brainer if she had never been stabbed, but we'll never know.
Serena's exploits are well known. Just a ridiculous player. 23 GS singles titles, 14 GS doubles titles, and 2 mixed GS titles. Her game is predicated by overpowering her opponents. Mansized serve.
If you go by the best all around player, I'd say Navratilova. Serena's double game is just power. Navratilova has all the shots and tactics, and she could handle the pace.
Best singles player it's just another argument. Graf is the best athlete and had a BH slice that would neutralize Serena's groundstrokes. I think in their prime's Graf beats Serena and Seles beats them both. You can't tell if Seles would of had the staying power or Graf or Serena, but she did burn bright before the stabbing. Another difference between Seles and Serena is the type of power they have. Serena hits more topspin than Seles did. Seles was killer off both sides and those flat shots ripped through the court. Seles was also more consistent than Serena. Graf on the other hand was the most consistent. So if I had to rank in their prime, I'd say Seles, Graf, Serena. If you account for longevity: I'd say Graf 1a Serena 1b, Seles.
I'd give the nod to Navratilova, because I value doubles in the grand scheme of things. It's all very tight though.
I will say this as well. PEDs are not exclusive to the men's game, which is a reason I don't like the Serena GOAT argument as much.