A year ago I did a fairly major update to the 321 Fast Play Napoleonic Rules rules, that included simplifying the charge procedure to speed play, and balancing units with regard to quality.
As always, rules can be found here:
Changes from Version 5.0 to 5.1 (March 2021)
Note: Even given the timescale of a turn (30-60 minutes),the ability of artillery to reposition it's firing arc, and swing around like a modern point defence weapon and fire (for example against a cavalry breakthrough) has been too great in terms of game effect. This change represents the inherent difficulties of reacting to breakthroughs with a deployed Napoleonic battery (which would also have an extensive train of limbers and caissons behind it).
Note: Squares automatically break if they lose to infantry. Infantry assaulting a town that don't break in the assault itself, just retreat, as it is assumed the garrison will not be in a position to pursue them (this was situation was a bit harsh otherwise). Lines failing to withstand a charge will probably break.
Note: Clarification that lances and obstacles don't help defender in a charging on situation.
Note: Adds Russian Guard Jager option
(1-2) Set Battle : Armies arrive too late in the day for battle, and deploy ready for the morning.
Starting with Defender, players select Divisions totaling up to a third of their units to start in reserve.
(3-4) Encounter Battle: Main bodies meet and begin battle, bringing up reinforcements.
Starting with Defender, players select Divisions totaling at least one third of their units to start in reserve.
(5-6) Escalating Battle: Advance guards clash over a vital position and call for reinforcements
Starting with Defender, players select Divisions totaling at least two thirds of their units to start in reserve.
Note: Ties reserve availability to size of game, you get more in larger games. Second point means that troops must be close to entry area rather than the entire table edge.
Note: Cossacks gain bonus to flank marching.