Breaks can be handled case by case, there's no need of a guideline, imo. No one want maps with unfitting or forced breaks and that's why mappers should be able to reason why they're putting shorter/less breaks. Also, the more wordy a guideline gets, the more confusing it gets to read.
About SV, is it okay for 299BPM, but not for 300? Better put it as a guideline.
And as a person who had no rhythm sense and spend a lot of time learning to play with Kantan and Futsuu, I support base SV regardless of BPM: usually faster songs have harder maps than the average, so low difficulties for those songs can be used as a "training" to learn to read faster maps while being light in note density.
Of course if the BPM go nuts (like 300BPM), small adjustments can be done, but always based on a guideline.
And there's the case that one could map a 150BPM as 300BPM, so ¯\_(ツ)_/¯
About SV, is it okay for 299BPM, but not for 300? Better put it as a guideline.
And as a person who had no rhythm sense and spend a lot of time learning to play with Kantan and Futsuu, I support base SV regardless of BPM: usually faster songs have harder maps than the average, so low difficulties for those songs can be used as a "training" to learn to read faster maps while being light in note density.
Of course if the BPM go nuts (like 300BPM), small adjustments can be done, but always based on a guideline.
And there's the case that one could map a 150BPM as 300BPM, so ¯\_(ツ)_/¯