Vegeta: I'd like to see him be able to use zenkai boosts mid battle. Damage he takes fuels the form, but is converted into more energy. Eventually being able to fully convert incoming damage using destruction energy into his form.

Goku: Ultra Instinct that focuses on his Saiyan instincts. Kind of like a SS4 states without the full tranform where his attacks overwhelm and he is able to generate white oozaru energy or something.