There are several variants that make C&C:A crunchier, but darned if I can point you to where they are now. I have just read them across a smattering of blogs, BGG posts, and such.
Battles of Westeros has some crunchy ideas that you might like. For example, you can easily take the flanking concept. The idea is that the first unit that combats an enemy unit places an engagement token between the two units. Any subsequent unit combatting that engaged unit counts as flanking and gets a combat bonus (can re-roll some combat dice). Being forced to retreat breaks the engagement, of course. Being engaged by an enemy unit breaks your engagement with another enemy unit. Voluntarily disengaging results in a Parting Blow, which is exactly what it sounds like: a free attack before you leave the hex.
Battles of Westeros adds more crunchiness by using Keywords – traits added to unit types which confer special abilities – each with their own special rules. It adds to the complexity as a whole, but if you study a scenario prior to playing it, so you can understand who has what ability and what the effects are, it gets more manageable.
Some units have the Formation keyword, allowing the unit to take a different stance in combat. Line, Wedge, Hedgehog, and Square are just some of those formations. During play you decide which formation you are using, for all units of that type, by flipping the unit's card over (one side has the formation and the other is normal). Rather than doing all or nothing, you might use tokens in order to indicate unit by unit. Units in wedges punch through the opposing battle line better. Units in line resist being flanked better. In both cases, these formations are more susceptible to range attacks. Hedgehog gets a combat bonus, but all attacks against it are also granted a combat bonus. Squares have fewer dice in the attack, but get more in battle backs and parting blows.
Some ranged units can get Indirect Fire, which allows them to fire on enemy units when tracing line of sight through an adjacent friendly unit. This makes for killer "triangles". (A term used in BattleLore and Samurai Battles, but I don't think is used for C&C:A because it does not use the concept of support in the same way – I think. It has been a LOOONG time since I played C&C:A. I mostly play BattleLore, which is a little crunchier, and Battles of Westeros, which is a lot crunchier.) As the bows can provide support for the two melee units in front, but still be able to fire, it makes the Tully Longbowmen very tough. If that weren't bad enough, they can also Volley, which allows a firing Longbow unit to get additional combat dice when firing along with their neighbors. (It is actually much worse than it sounds.)
By the way, you can download all of the rules for Battles of Westeros and its expansions for free from the FFG web site. Even without the game you can glean a LOT of information from those rules. If you download the Vassal module, you can get even more information.
So, we have covered Battles of Westeros, now we go to BattleLore. BattleLore uses a concept of support (having two friendly units adjacent) in order to confer the ability to: a) ignore one flag, and b) battle back. I realize that C&C:A allows you to battle back anyway, but as you are mucking about with the rules, why not change that one? This forces the player to maintain battle formations or risk destruction as they are hit by units and cannot hit back. I see more line breaking, rolling up the flanks, destroying isolated units, etc. in BattleLore than I did with C&C:A, which is why I moved away from the latter in favor of the former.
BattleLore also has Lore, which most people think is magick, but that is not quite true. Yes, it does have cards light Fireball and Chain Lightning, but it has a number of cards that are simply unit buffs (attack with +1 dice, ignore one Banner hit, ignore all Flags, etc.). There is a variation in BattleLore called Medieval Lore that uses only those Lore cards that are not "magicky". So it allows you to use the unit buffs and apply them at critical moments in the battle, but it does not overwhelm the game.
Again, all of the BattleLore rules can be downloaded for free from FFG and the Vassal module has all the information you would need. Despite being out of print for awhile now, eBay has copies for sale and the BattleLore on Vassal community is currently running tournaments with a dozen players.
Some other ideas I have read involve having the units face a hex vertice and then using movement to change facing, and adjusting the combat dice based on whether you are attacking to the front, flank or rear. Others have adjusted the dice for attacking on the flank or rear, meaning units are destroyed faster. Some use both ideas in combination, but that seems to be double jeopardy.
Anyway, I cannot remember where I saw that, but it might have been in one of the rules sets from the Tin Soliders of Antwerp.
Hope something here spurs the imagination.
Dale