I was thinking about "wrapping 1K, 2K, 3K, 4K until 10K" in 1 customizable mod: Key count ! Customize settings: Number of keys It's a scroll bar from 1 to 10
Combining individual key mods into one has been proposed before but has wide ranging implications on the rest of the osu! infrastructure (the website for certain, possibly also stable). So it's not something that can be done very easily.