The Nationals should absolutely plan on resigning Josh Bell. He is a good 1B. He won't be cheap, but he isn't going to cost so much next offseason that he'll be a major factor in resigning Soto.
Josh Bell will be a good slugger for a while. Resign him. Have him behind Soto for a few years.
If he repeats his May 9 - present performance, Bell will easily command 20+ million AAV over the course of 6-8 years