Firstly we were only looking at the later period where only loose order troops are available to armies. This is helpful as it means that we only need one infantry speed. We took as the basic move unit one square, and applied that to both infantry and skirmishers. Artillery moves at the same speed and we had cavalry move at two squares. This is a bigger difference than in the normal game (which gives a ratio of 1:1 1/2 for movement rates, infantry v cavalry), but I think it works okay.
For the movement modifiers we took a simple approach again. Roads give an extra square of movement regardless of troop type, woods or towns require loose order infantry to take an extra turn per square, and streams (which run along the edges of squares) take a move to cross.
Turning has to be by increments of 45 degrees. You get one free turn of 45 degrees (or an about face) per bound (infantry are the only penalised troop type any way) and any other turns take an entire move. We haven't bothered making adjustments for moving on diagonals, and frankly didn't notice any problem.
Firing ranges required a bit of twisting to make them fit, but we're helped that when defenders are charged they always get to shoot. This means that you can extend some ranges without unduly penalising some weapon systems that don't get the extension. We ended up with:
Smoothbore Muskets - 1 square
Rifled musket/early breechloader - 2 squares
Later breechloader - 3 squares
Smoothbore artillery - short range 1 square, long 3 squares
Bronze rifled artillery - 4 squares
Steel rifled artillery - 5 squares
We used slightly longer ranges for artillery in our play test, but I think these are closer to the move/fire ratio in the rules. Skirmishers get an extra square's range, regardless of weapon. You'll note that in the original rules smoothbore guns outranged later rifles. Now they don't. I think that's okay
When looking at fire arcs the basic 45 degree rule works for squares okay, but the Peter Pig rule of only allowing one diagonal when counting range works as well. I prefer the latter.
Before going on to talk about the hand to hand rules, just a quick discussion on square sizes and occupancy. We were using 6" squares with figures on 3cm frontages. Those square sizes are too big, or the bases are too small, really, and affect the aesthetics as much as anything. Hence we deployed infantry in a single base depth line, and allowed two columns per square. On reflection I should have used my mat with 8cm squares, and allowed one infantry/cavalry unit per square. Infantry can share a square with one gun, or you can have two guns per square (or maybe three? not sure).
If you go for the bigger squares then two infantry columns, one infantry line and any number of guns up to a maximum of three units in a square is okay.
For hand to hand a unit must have enough move distance to be able to move into the attacked square. The only other issue is the loser retreats rule, which simply translates to one square. Otherwise the rules are unchanged with only one unit allowed to contact per face. If a unit is coming in on a diagonal, move it to the front square if there's no unit there, or the flank square if the front is engaged.
With bigger squares, and two infantry columns per square, one attacks, and the supporting column adds one die per base left in the unit. In our playtest this gave the Russians a prayer of making a successful assault, but not much of one.
These changes create some distortions. I think you end up taking an extra turn of fire when charging the front of a unit generally, so perhaps you only have to be able to move into an adjacent square in order to melee the defenders, but still allow the defensive fire rule. Yes, that sounds about right.
We need to revisit these ideas next time we play, but they seem to me to work and they speed the game up, especially when there are a lot of units on the table.