Jason and Lucia being a couple is the canon way of playing GTA VI.
I know Rockstar Games has basically said making the two leads a romantic couple is optional, but let's face it - and pretty much all the trailers have shown it - there is such thing this time as a proper way of playing the story mode of GTA VI. Jason and Lucia must be played together as a romantic duo if we are going to get the proper experience and emotional impact of the upcoming game. Otherwise, I don't think this game's intended messages and true appeal will be missed out on by many gamers.