Grouping & bpm are already available using smart playlists, right click on any smart playlist to start a new one
You can change the way the library sorts, by clicking the wrench next to the search box
Click on any playlist header to sort by that criteria, click again for inverse order
Right click any playlist header to change which are displayed, drag n drop to change the order
You can add a keyboard shortcuts to change the shuffle mode & a bunch of other things
I don't know about play counts or ratings. They are player files & in their own database, having no universal format may not be cross compatible
I stick with fields that are metadata, comments & grouping, which follow the files, not the player
Clementine is developed on git hub, feature requests & bug reports are handled there