Tuskmod, the Steam workshop edition.

Tuskmod is a full revamp to the games basic mechanics, a rebalancing of its units, and a partial retreading of the campaign as well. Focusing on deep, difficult, and fierce battles, expect tuskmod with submods to use fewer autoresolves at the very least.

The summary of features is a constantly changing animal for tuskmod, but tuskmod always focuses on the same goal of providing a game that feel like it is alive for longer. In doing this…
Tuskmod has won the 2015 "Best Overhaul" award.

New Mechanics:

– Innitiative: Functions similar to, but not identically to a reload skill for melee attacks. Blunt and piercing weapons have very high innitiative scores, allowing their units to fight unusually well in tight formation.

– Accuracy: This attribute hasn’t really been used much since shogun 2. No, seriously. Base Attila, all accuracy scores were 0. Tuskmod fixes this by… Simply re-implementing it. Elite archers will actually hit their targets more often then levies.

Campaign tweaks:

– Basic unit rosters will be availible sooner in the campaign, giving the player, and the AI, a chance to make more interesting army early on.

– (Submod) Dynamic garrisons makes it so city battles are very often worth fighting, as the garrisons will be pretty well equiped, and fairly large.

– Stupidly overpriced units have been made not so.

– Huns have been tweaked, they come in fewer, more threatening waves now.

Tweaked Mechanics: (Incomplete list.)

– Impact and the Charge: Charges tuskmod focus more on charge bonus then mass. This is important, as….
— Vanilla charges did up to 80% of their casualties in the impact phase…. When charging light cavalry into medium infantry.

– Formations: Formations walk faster, and in general, are much better at preventing a unit from dieing.

– Loose Formation: Loose formation has been tweaked to actually reduce casualties from missile fire.

– Units decellerate much slower, and men are a bit wider, causing them to compress in interesting ways when colliding with obsticles… Or other units.

– Units fatigue fairly quickly out of combat, but only moderately fast in combat, making proper fatigue management vital to getting the most out of your units.

– Unit sizes vary more, expect to see melee infantry to commonly have unit sizes as low as 75/100, or as high as 135/180.

If you wish to uninstall tuskmod, and keep your old saves, the legacy fix is your friend:
http://steamcommunity.com/sharedfiles/filedetails/?id=441468966
You will still need to keep all garrison mods you have installed on that save, but the legacy fix will help the game transition back into its normal state in most if not all cases.

If you are having issues with recruiting advanced units in the last roman campaign…
http://steamcommunity.com/sharedfiles/filedetails/?edit=true&id=552139393
This submod will solve your problem. The unit obsoletion tree for the last roman being enabled was causing certain units to become prematurely availible in the grand campaign with the new recruitment changes… This of course was a serious balance issue.