The only functional use I see for a belt is as a tangible diploma that you can later leverage into credibility when you open your own gym. For that reason, your belt is not just a reflection of your skill level but also of a grasp and understand of a specific curriculum.
Within that context, getting a belt without the guidance and oversight of a specific instructor is kind of meaningless since you're teaching might not be a representation of their school. If I were you, I would find what system or school I want to rank under and then make monthly or bi monthly treks to that school for privates where a lead instructor can monitor your progress and refine your game within the parameters of their curriculum.