...both as a fan and a student studying game development. Even if Gamefreak had the resources for it and the cartridges (3DS or Switch) were capable of it, I feel like it would break the core concept of what Pokemon games are; starting from the bottom and making your way to the top. In theory, wild Pokemon could adapt their levels based on the player's current levels but it would just feel...wrong, to me.
And I know that in the anime Ash left his Pokemon behind with Oak (at least in Gen 3 from my knowledge), and I think this would be fine if the game left you retrieve said Pokemon once you reach certain areas (eg. you can withdraw Pokemon at level 30 once beating Gym A and being able to enter Route B) but it would still feel different from what a Pokemon game is.
To me, the ability to return to Kanto after completing Johto feels like a one-off. A sort of tribute that shouldn't / won't be repeated just yet.
And I know that in the anime Ash left his Pokemon behind with Oak (at least in Gen 3 from my knowledge), and I think this would be fine if the game left you retrieve said Pokemon once you reach certain areas (eg. you can withdraw Pokemon at level 30 once beating Gym A and being able to enter Route B) but it would still feel different from what a Pokemon game is.
To me, the ability to return to Kanto after completing Johto feels like a one-off. A sort of tribute that shouldn't / won't be repeated just yet.