The Toyobaru gets a little bit of flak in the press for not looking as beautiful as it could. EverydayDriver—my favorite video review guys—remarked that "it's a 7, maybe an 8, but it could have been a 10; this is a car that's starting with a blank sheet of paper." But is it, really? I think there's more of the 2000GT in this design than meets the eye.
These graphics are part of a little presentation I put together to explain the BRZ's design language to a friend of mine, who happens to be an industrial designer, but I think it's a pretty comprehensive breakdown of every line that Toyota's styling department cribbed from the 2000GT.
As you can see, most of the obvious cues that relate the 2000GT to the Toyobaru are visible in profile: the pointed window (the most obvious and/or harped-on cue of them all), the shape of the door (which is actually a subtler reference to the 2000GT than most people give Toyota credit for), and the wheel arches. In the case of the rear wheel arch, it's not just the flare that the Toyobaru inherits; it's also the the relationship that the rear wheel arch has to both the roofline and the pointed rear window. That relationship results in some very complex surfaces on the sheetmetal; this is explored in more detail in the next graphic.
As you can see, the shape of the pointed window works together with the sweep of the roofline/C-pillar to suggest a pronounced downward swoop; this is sort of "intercepted" by the flare of the rear wheel arch, and as a result, both the roofline and the wheel arch flare "level out" rather gracefully at the rear reck. (Also, take the Cayman comparison with a grain of salt; I was mainly using that car as an example of coupe design for my friend's edification. That would come out in an oral version of the presentation.)
Here's a sort of design-cue easter egg that it actually took me a little while to notice: the BRZ has a kind of double-bubble roof that, while not nearly as pronounced as, say, the Viper's, pretty transparently draws on the 2000GT's roof. From this head-on view, you can also see that the pronounced flares on the front wheel arches also have some precedent in the 2000GT. You might also notice a very subtle crease dead-center on the 2000GT's hood; this is clearly echoed in the way the Subaru/Scion/Toyota emblem leaves a "bulge" in its wake, in the same central axis of the hood.
Note also how the rear deck is sculpted on the GT86. It slopes upward in the center, just like the very gentle upward curve in the middle of the 2000GT's rear lip spoiler. Very subtle, but definitely a nod to the old Toyota.
...and, as a bonus slide, here's my commentary on the BRZ's headlight and taillight design, which is marvelously cohesive. As you can see, each shape comprising the headlight has a corresponding shape in the taillights, and that really makes the design symmetrical—as though much care was taken over it. Sometimes, it's the little things.
It's possible I'm overthinking this. But I see the Toyobaru less as a "missed opportunity" for a new and beautiful design, and more as a very modern, very thorough homage to the 1967-70 2000GT. A LOT of this car's virtue lies in its "old school" character, and part of that is surely based in design.