Would an area-ruled fuselage improve the MiG-15/17's performance? The top speed range of these MiG 15-17 airplanes is in the transonic region, but, when they were first designed, the area rule was unknown.
Even if owning a jet fighter is not exactly 'Maintaining pilot's performance', thus hard to obtain or license, the change looks not too complex to implement; curiosity, experimenting, is the force behind Aviation progress. Salut +
In a word, yes. But that sort of depends on the definition of "performance". The top speed would likely be effected only in a minor fashion, but the transonic acceleration would likely improve, as would the fuel economy.

It is worth pointing out that, largely by luck, many of these aircraft got some of the benefits of the area rule without specifically designing it. The location of the cockpit behind the intake required the fuselage to become larger in that area, especially when one considers the canopy, which ends just in front of the wing. And then the tail begins near the end of the wing and the fuselage begins to narrow behind the engine as well.