A cool feature for DoF would be to let people create their own formations.
A way to do it would be to let a player set specific areas for specific units, such as, ranged units will be in the area designated for ranged units and melee units will go into their designated area etc. and then the player could name their new formation and have a button in-game that could be that formation, or there could be a "Custom Formation" button that opens up to show all your custom formations.
Also, if this is implemented, It would be great if you could have areas that apply to multiple unit types like: an infantry and/or calvary zone, and the player could choose to have both or have one unit type preferred. Like, if you had infantry and calvary, and you choose a formation that has an infantry and/or calvary zone, then the preferred unit would go there and the other unit would go to another area in the formation.
Picture made by Aametherar the orc (Elves are the best!)