Moving outwards, Yari and Te Yari units, perhaps the odd Sohei, will be fighting each other. Whoever breaks first will be able to flank and undermine the center, caving the whole center inward, the ultimate goal of battle.

Teppo units sit on the flanks, firing at each other and raking the opposing flanks. In early, the No Dachi and Naginata would be flanking the enemy line, but the advent of Teppos make their job nearly obsolete since they accomplish the same thing but require less training and casualties. Charging Teppos may be done, but it will be costly; Nagashino being a prime example. The flanks will be very fluid.

Cavalry will be trying to circle wide and fight each other with the ultimate goal of causing enough fear ti start the rout of units. Takeda, possessing special shock cavalry with an additional morale reducing trait, are especially good for this.
I'm very sorry if I sound rude but have you ever played any Total War Multiplayer?

"Teppo units on the flanks" - I think, they would be too far away from protection by Yari samurai if the enemy cavalry charges them.

"caving the whole center inward, the ultimate goal of battle." - I think the ultimate goal would be to break the enemy's morale.

"Cavalry will be trying to circle wide and fight each other" - why would they want to fight eachother? I think, they can and will be used to devastating effect by quickly circling round the fighting infantry and attacking them from the back.