It depends on what you mean by RWYB. Traditionaly it done with the following requirements:
1) It has to be a kart.
2) No minimum weight.
3) Minimum age – 16, 18, or 21 – depending on what your insurance says.
4) A maximum engine displacement – 250, 350, 500, or 600. Again insurance dependant.
5) No restriction on body work except for overall length, width, height.
6) Standard safety requirments for brakes, safety wire, etc…
If you want to try to equalize the various typs of karts, good luck. The only one that is roughly equal is that a CIK Sprinter with a 250 single on it at 385 pounds is roughly equal to a 250 ICE kart at legal weight. After that all bets are off.
A class like that is usually just for fun which is good because you’ll never make it “fair”.