The capabilities of your League app seem to be easily accessible via multiple other apps (porofessor, op.gg, League client itself), and during pick/ban, suggesting champions/runes to use based purely on community stats may actually be detrimental (the player may be much worse at a suggested counterpick, than if they just played their best champion).
I think if the coach client can provide suggestions such as the following, it would provide a lot of utility for minimal effort: 1) reminder to check mini-map 2) after a kill, suggest backing vs. pushing wave to tower vs. roaming 3) itemization suggestion, which has a more objectively optimal choice based on team comp/itemization than champion selection.