My comments on experience and marching/maneuvering:

It would be great to see an effect in normal march speed and order during march; both while running and walking.

Also, if my sources are right, the formations tended to slow down more and more the closer they got to the enemy. This isn't probably factored into the game, but it would be a nice "added" flavour. Experienced units would march faster even at a closer proximity to enemy lines.

Another thing I'm curious about is the formations' effect on morale. In Total War games it has usually been based more on flanking and local/global numbers, plus the general. There are other aspects that would be nice to accommodate: for example, rock-paper-scissors due to unit types in certain formations. For example, a loose formation vs. cavalry closing by might cause a rout pretty quickly, unless it's an experienced unit of light infantry. The square formation is pretty simple: it is difficult to flank. Tightly packed columns reassure men.

On the one volley, then bayonets assault: sometimes the enemy infantry broke already when they saw the attacking infantry attaching bayonets.

On cavalry charging against formed lines: bad idea.

Against a fully organized line it was difficult to charge an infantry line. First of all, at 30 paces the volley caused lots of casualties, and broke the tight formation, which meant a weaker overall mass of the charge. Also, at such close range, the second cavalry line didn't have time to fill the gaps, and tripped on dead horses. Thirdly, the tightly packed line formed a solid spear wall, which was naturally more difficult to charge, especially as lances weren't used too often.

Cavalry charges usually didn't work against well-formed infantry lines, that is why the charges were usually set up with cannon fire/continuous (i.e. free) light infantry fire and other combined arms operations, or by other infantry units. Skirmisher and cannon fire caused gaps in the organized lines (which enabled cavalry to charge the corners of a less-organized infantry square). Under pressure and under constant casualties (and sharpshooters killing officers and NCOs) an organized volley was difficult to pull off, and weakened morale meant that the enemy broke easier even before contact.

An infantry unit engaged in a melee with another infantry unit, or engaged in a firefight, was a better target, but of course you should flank if possible.

However...

Things aren't that simple, though. When we talk about larger scales, i.e. a cavalry regiment attacking an Infantry Battalion, the situation is different. Consider a cavalry regiment in a column attacking an infantry battalion in a line. An infantry unit formed into a line may cause large casualties and break the first 1 or 2 waves, but the following waves usually manage to hit the line, and cause large casualties, often causing a rout in the localized area. If the infantry is in a column, even if the first three man line is broken or pushed back, the men behind it can still fight the cavalry off. Also, the tighter column formation is more reassuring, and the tightly-packed men feel safer.

An infantry column attacking an infantry line in melee works supposedly the same: 3-man deep line is relatively thin compared to a huge mass of men running at you with their bayonets. Of course, such a formation is an easy target to infantry fire, and there will be lots of casualties.