We almost exclusively use number charts for chords on our confidence monitor so our instrumentalists can play in the key of their choice (and capo or transpose to the actual song key).
Currently, you can only automatically pull ChordPro data from SongSelect CCLI if it is key-specific, which means we have to manually edit every single lettered chord to be its number equivalent. It seems that the ability to automatically pull in number ChordPro files should be pretty straightforward to add and would certainly be a big help to our workflow.