With the national dex not coming back in SwSh, I'd like to go through and finish each generation's pokedex separately. I'd be willing to use any remakes to finish the pokedex, such as using ORAS instead of the originals if I have to due to events not happening anymore, and I'm not looking to complete the national dex in each game. If possible I would rather not have to trade between generations, but trading between same gen games is fine. I'd just like to know what games I would need to finish this, any help would be appreciated.
For the generations that still have the Nintendo Wi-Fi option (Generations 6-7), I'd recommend trading with other people for Pokemon you don't have. But if you must, having access to all Generation 4-7 games should be enough to complete the Pokedex. You may have to restart some games to pick different starters, but it's definitely possible.