I think this applies to a greater or lesser extent to all the players. I mean, a few are quite smart and have college degrees or some such, but at best this would get them some nice corporate job with a company car, but nothing remotely like the astronomical amounts they currently earn.
Anybody who thinks that any of these women would have made a successful career in fashion design/acting/modelling/etc. without the fame they have achieved in their tennis careers is in serious need of a reality check. Pastry chef sounds about the right level for most of them.
I don't agree
Actually I think that many of these women would be successful in any job they would choose. They got where they are not only by having a tennis talent. It was an important factor, but more important was hard work, dedication, great work ethics, making smart career decisions, finding right people to train them, sponsor them, managing their affairs etc. They've managed to avoid the usual traps waiting for very young people who make good money very quickly, so they have a lot of good sense. They also know how to pursue a goal and they like winning.
You are right saying that they wouldn't probably make such money as they are making now, but I believe that many of them would have good, interesting careers. Maybe even as pastry chefs, but with their own chains of restaurants
And as for other posters referring to Aga, most of doctors would tell you that the most important thing in their education was hard work, learning by heart of thousands of latin names, symptoms, chemical formulas etc. plus practice, practice and again practice. So I wouldn't count Aga out as a surgeon.