Appreciate the thought put into this post.
I would project Bellinger for around 3.3 WAR next year if he can stay in RF the whole year, plus he gets some added value tacked on for being able to play 1B well plus the other OF positions as backup, which doesn't show up in his WAR. I'd project Soto for around 6.0 to 6.5 WAR, So Soto adds about 3 wins to this team over Bellinger. He'd be a very nice addition but yeah we need more improvements, we'd still only be about an 86-win team which is still a borderline wildcard team.
Catcher, SP, the pen, and ideally another bat upgrade somewhere definitely look like a priority.