Yeah, I've asked for Bone Groups before and would still like to see it. It was actually one part of a two-part request. The first part of my request was the ability to define a group of bones so I could easily select it, and the second part is the ability to keyframe the visibility of the group, another thing Moho doesn't currently do out-of-the-box.
Some the reasons I wanted these features have been addressed to through other means. For example, I wanted these features so I could set up a sub-rig swapping system more easily than I could using Victor's old rig-swapping method, and Vitruvian Bones was the answer for that. I also wanted to be able to temporarily hide certain bones and reveal them with a shortcut or button. Shy Bones does that, and my MQC panel provided the button I wanted.
That said, Bone Groups and keyframeable bone visibility are still on my wish list. I can find other uses for these features not addressed by the above.
In the meantime check out these two scripts. They
might address what you need right now...
Bone Selection Buttons by Stan. Let you select groups of bones by assigning them to buttons. The sets are unique to each bone layer and you can even import/export the settings.
Toggle Bone Color by Lukas. This one groups bones by bone color and lets you keyframe their visibility. This tool technically does what I want as described above but I like to use bone color for other things, so I don't use it that often. But when I'm not hung up about using bone color for other reasons, this tool works great!
Hope this helps.