One talented Pokemon fan has modded HeartGold & SoulSilver to include Overworld encounters, and trainers are dying to play it.
Pokémon HeartGold and SoulSilver Concept Art & Characters, heart gold pokemons
Pretty happy with my rework for wild encounters : r/PokemonROMhacks
HG/SS Random Wild Pokemon Encounters and Levels AR Codes
Pokémon HeartGold and SoulSilver - The Cutting Room Floor, heart gold pokemons
Pokémon Heart Gold & Soul Silver - New Areas, heart gold pokemon league
Pokemon Heart Gold & Soul Silver, TM Locations, heart gold pokemon locations
Pokémon Heart Gold & Soul Silver - Trainer Rematches
Nintendo Files Pokemon HeartGold And SoulSilver Trademarks, But, pokémon heartgold
Pokemon Heart Gold & Soul Silver, TM Locations, heart gold pokemon locations
Pokemon modder adds wild overworld encounters to HeartGold & SoulSilver - Dexerto, heart gold pokemon locations
Let's Play Pokemon: HeartGold - Part 30 - Elite Four Karen , heart gold pokemon league
Pokémon Heart Gold & Soul Silver - Your Partner Pokémon, onix pokemon heartgold
Pokémon HeartGold & SoulSilver - Champion & Red Battle Music (HQ) , heart gold pokemon