I like the Unreal Tournament idea
every character has a Name.
you get a little menu when pressing X(Orders)
in M&B it would divide into
FORMATION
select names (with checkmark) from a tabel that has information about them (else youd have to remember who is who... think of 20 ppl in your army!)
then select formation (square, lines, diamond, hollow square...)
MOVEMENT/ORDERs
select names Or a Formation, and order them to move to nearest hill, river, attack, defend, follow me, retire(goes back to start location), regroup(also needs MORALE implemented into the game.. tries to regroup all formations at the start location), hide (would require SOLID OBSTACLES, eg in City Siege..), assault....
OTHER
mount of horse(select who, and on what horse, if none selected hops on his own horse), dismount, and some others...
Selecting has possibilty to select all with same horse speed/same weapon/ or horsed/unhorsed/ranged/melee... and of course ALL