I agree Sato is the most interesting alternative and also mentioned him upthread, although it’s not a guarantee he gets posted.
With all the caveats about not knowing what happens with the next CBA, I reject the premise that the $42M is a limited pool and that another $42M couldn’t be spent even if Bo stays.
But even if Bichette were to leave, and the team spends that now-freed money elsewhere, it’s true they don’t have to improve at third necessarily. If he leaves, third base will become one of the 4 spots in the everyday lineup open for improvement (with first, second, and OF/DH). Yet even with such open flexibility, I’m still not sure there’s a realistically available player I like more than Bichette for any of those 4 spots. I guess Brandon Lowe is intriguing as mentioned above but I’m not sure he’s a better option.