I think that it should be based around all the johto pokemon, the evolutions and de-evolutions, they should then bulk up the pokedex by adding pokemon from all the other regoins, the majority being kanto though as it is likely they migrate between kanto and johto!
pokemon such as houndour and murkrow should be found earlier in through the game!
pokemon such as houndour and murkrow should be found earlier in through the game!