I never use the pocket - I've seen it break too many times on me. I seal the end of the bridge with spear infantry or pikes if available, and I have heavy infantry behind the spears for when the enemy is committed and a pocket is still starting to form.

Behind that, I'll have missile units. Bows or crossbows - gunpowder just kills your own people. AP missiles like longbows and crossbows will do tons of damage to the incoming enemy. If I have javelins or naffatun, I'll put them in with my spear line. They will wreak havoc there.

I place cavalry off to both flanks, as broken enemy units sometimes run to the sides. Also, when the enemy army breaks, they are closer to capturing them. If the enemy doesn't break, you can swim light cav across the river to hit them from the rear for a complete massacre.

Artillery of any sort is placed farther back, but in line with the bridge. Bouncing cannon balls are just freaking wicked nasty, I actually had one cannon ball take out two generals on different bounces. Any extra artillery I'll put on the shoreline to the side of the bridge to act as counter-battery and soften up the enemy, but they don't get as many kills on the bridge so I don't bother letting them shoot there.

As mentioned, pike units tend to stop charging units cold, until they are able to filter in. Naffatun are absolutely insane in this situation, as their grenades will take out huge numbers of units and rout the rest. Handgunners are pretty decent too, I've had them break the charge at the last minute and still mop up the enemy, but they need good armor upgrades for that.

I'd say though that longbows are probably the king of bridge battles, followed by artillery.