You have my total support on this.
Since Taiko and CtB communities are growing more and more, there's going to be lots of Taiko and CtB maps (yeah, since CtB maps are now rankable) in the future (already lots of taiko maps, though xD).
So, in order to spare hundred hours -for each veteran player that does NOT delete maps- looking for a Taiko specific map, or a CtB specific map, we need this.
This also applies, like said in the topic, to osu! players. They don't want to play a map with Taiko/CtB, just the main game. So they won't have to delete each taiko map in the mapset in order to play peacefully with no surprises or things like that.
I'm really sick of browsing each mapset just to get the Taiko diff when I want to play. Even with keywords sometimes I don't find most of my taiko specific maps.
So, this must be added, as it will save lots of time, work, and fun in the game. I gave you my votes, twice, 'cause one is not enough, and that I don't have more to offer. But if I could, I would give them all to you.