" 1) I nearly always end up being outflanked because the enemy deploys in a single long line without any reserves; "

to aid at this...adjusting ones tactics might be enough...no modding necessary.
every battlefield is different...terrain, units, weather, numbers, commander, blahblahblah...tough stuff...

in general though...assuming an equal enemy with mostly phalanxed units, little or no archers...and a mostly level terrain...(xs and 0s for peeps and just lines and directions, and (X)s, (0)s are cavalry units for flanking)

attack one flank of the line with nearly everyone head on and close together...if timing is right then u hit them in force where they are weak and u can adjust more quickly while they are spread wide and have to collapse in, it gives u a nice window to flank appropriately while they are compensating for being spread too wide apart...and u can deploy some in a manner to avoid being flanked considerably...as they are as a whole collapsing in not spreading out...
i could be wrong but it seems like under relatively equal conditions, timing and moral are the 2 most important factors in winning or losing...




(0)
(0) (0) (0)
0 0 0 0 0 0 0 0 0 0 0 0

^
^
^ ^
^ / ^
| /

^
X X X /
X X X X ^
(X) X X X /
(X) X X -->
(X) (X)



works for me, but i dont know if that can help, but perhaps it shall help someone who has troubles in similar battles.

good luck with the mods.