Are you going to let your car define where you go or let your driving needs define the car you pick?
Your thought that "With many of the square formatists I look at however, their chosen frame format defines their aesthetic" is in my opinion backward. I think that their chosen aesthetic drove their frame format choice. I.e. they bought the car that fit their driving needs.
I would also suggest that there are many photographers who use a variety of formats successfully. I know some of these guys personally. One, as far as I know only has two cameras, an 8x10 and an iPhone. Another does digital at his day job and 4x5 for all his personal stuff. For both the work they do with each camera is very different, but both sets of work for each are great. For both their camera choices are defined by the result they want in a given setting.