Nice idea, thanks for that! Never really thought of doing that to be honest. You're right about coaches - does seem to be a waste of time.I'll tell you right now that coaching means nothing in lower leagues. Don't even bother with it, you don't get many coaches, or any good ones that would ever really improve anyones stats. Most of the players you get while in Lower Leagues will be gone by the time you are promoted a league or two anyway, so it's really a waste.
Focus on getting coaches with high Scouting Ability, as it is easier to pick up a good scouting coach in lower leagues than it is to find an actual scout. And since you probably only get two scouts, the extra coaches can put together quality scouting reports for players who may help your team get promoted.
Also look for coaches who expand your scouting knowledge, as this will help in your search for talent.