I'd like to add, that some patterns in CTB are easy and ridiculous in standard mode.
(For example
O__________
O__________
O, stream jump at for example 320 bpm, hyperdash system lets players catch it perfectly)
And... many technics, type of sliders (Burai sliders, etc), various inconsistent spacing (CTB does not care about distance spacing), slider velocity changes, hidden notes (except hidden fruits in spinners) All these technics are unrankable, but i think perfectly rankable for CTB. Of course CTB has another extra things, like some patterns in CTB are impossible (ridiculous to get), but perfectly possible in standard mod. Such things like: very fast sliders (Banned Forever, Nogard difficulty, DJ Sharpnel - StrangeProgramm, Lesjuh's Tag difficulty), offscreen droplets.
I can link tones of maps, that have CTB bugs, if it is really needed, i'll do that, amount is great.
The current reason for CTB difficulties being unrankable is because they are not necessary since standard maps convert well into
CTB patterns, which is not the case in taiko and thus why taiko difficulties are allowed to be ranked.
(Why this was not deranked, seriously), etc.
I'm sure, that Catch the Beat-specific difficulties should be
allowed, because osu!standard difficulties convert to Catch the Beat difficulty not well enough, due to some bugs.
And i see no reason, why it shouldn't be allowed.
I actually support CtB difficulties. What flows well in CtB isn't all the time good in osu! standard. And some maps are really boring in CtB, while they could be quite fun with a CtB diff.
However, we do need a set of guidelines and/or rules.
viewtopic.php?f=13&t=55363 i think there is written everything about guidelines and rules, nothing to add.