The Shodokan system does as well. Although the bulk of the lesson everybody practices togeather with a senior student paired up with junior (ie. 5th dan with 2nd dan, 5th kyu with 7th kyu, or some such mix) there are techniques concentrated on depending on what grade you have achieved during every class. Quite a lot of thought went into what's introduced when - Tomiki was an educator after all.
That said - rank is an organizational mechanism nothing more. My class is so small I haven't held a grading - there is no real need but I probably will eventually. The kyu/dan system was introduced as just that - there was no deeper meaning.
And to tell you the truth (vis a vis the last post) I have yet to meet anyone who trained just to get a belt. I have met people who wanted to do a certain budo for a defined length of time before trying something else. Shodan was a convenient marker and who am I to question that.