You can level your Gastly until 99 cause Haunter needs trade to evolve not lvl up... >.>, you should know that.
Edit: whatever this game isn't a GameFreak game or something like that, It isn't a exactly copy of the pokemons games, things can be changed, This is a game of Revolution Team, they can do what they please if you want something else you can do some usefull recommendations etc and if they WANT do it they will considerate that, you CAN'T obligate them to do what you want, i'm not referring this to the person I quoted it is just for everybody that want this game to become what they want, Is it hard? yes, it is and I like it if you want easier of faster game go play official games.