Actually, aside from Koga needing to serve as both an E4 member and a Gym Leader, you also have to consider that Gen 2 had Blaine in an entirely different location, Giovanni was the 8th Gym Leader (and left), and Blue (champion in R/B) replaced him. There's a lot you'd need to take into account when combining the 2 gens. Gen 2 also gave Kanto Gym Leaders access to Pokemon they'd never had in Gen 1 (which is justifiable in some cases, but not so much in others). Herp makes a good point.