I may be wrong on this, but I believe unit settings are provided as backup; the formations do override any settings made (except digging in).
The cases where it fails is when a troop leader isn't there and the settings are used (which would not be resolved by your FR) or where a troop leader doesn't like his formation options and chooses to set none, handing out custom orders instead. The flexibility you request here solves that problem quite completely.
Though, I kinda feel like a similar, also cool idea might be to add special benefits to the existing formations. Maybe a small advantage to offense or defense, or a resistance to a particular unit type? We know how to hard counter these with strategy, but it might be cool to have different, unique uses for the presets (so they don't fall into obsolescence themselves).