I'd prefer more GSC hacks as I'm a die-hard GSC fan.
But if I was to be honest, I'd like to see something similar to Pokémon Conquest, but under a main series game format, the main character themselves can only have one pokemon at a time, and any others caught would be sent to your PC automatically. (So practically everyone has just one pokemon, but you can always switch that pokemon out for another you have caught and was sent to your PC)
Instead of having a party of six pokemon like a normal game would, you'd instead recruit pokemon warriors (humans) with their perfect pokemon connection throughout the region during your travels. And you would be able to have a total of 5 pokemon warriors besides yourself to join your team. But only you have the power to switch out pokemon, because no one else has the power to have a perfect connection with every pokemon, including legends.
And just like Conquest. You fight with your team to claim land in the region. But in the storyline, you also face a great evil in the form of a tyrant. Etc, etc, but hopefully you get my point.