I agree that lenses are more important than cameras, in general, but once you get lenses of a reasonable quality, then putting some money into your bodies makes sense. You can shoot sports, e.g., with a non-motor-driven FM2n, but you might have an easier time of it with an F4s or F5, with AF and a motor drive, and you might have better luck with accurate exposure in rapidly-changing light conditions using autoexposure.
I'll tell you one thing I really prefer about the F3HP or F4s versus an FM2n (and I own all three) - the high-eyepoint viewfinders. I wear glasses, and using the first two cameras is a lot easier. Still, the FM2n is a great camera in its own right, and it's awfully reliable in the cold, since it doesn't really need the batteries except for metering.
These days, with film cameras being so cheap, a person can afford to have the best of gear. I can't justify owning an F5 from a purely practical level, but the price has dropped to such a point that I can afford it and get my money's worth out of it. I really don't care if I need it or not.
Henri Cartier-Bresson made a career out of using a simple rangefinder camera and a 50mm lens. Should everyone have such basic gear? Obviously you can do amazing work with it. Photography would be boring, however, if everyone used the same gear.
Don't forget the glass - it's hugely important - but as long as you can afford reasonably good glass, by all means get reasonably good bodies to go with it. And, especially if you are a film shooter, have more than one camera - for multiple film types, not having to change lenses (sometimes subjects don't let you change them - there simply isn't time), and for the pleasure of using complementary tools.