Basically I came up with this idea for the OMG mod and it evolved into their ability to load units into HT from the launcher. But it is my belief that the American Armour doctrine is currently lacking in most regards as to unit diversity and capabilities; my proposition is the inclusion of the Armored Infantry or Mechanized Infantry. These units wound fight basically right next to allied tanks and protect them from the various axis anti tank weapons that have really reduced the capabilities of the armored doc.
These units would not necessarily be elite infantry but more of a mechanized form of the rifleman that gains significant bonuses while around tanks or HTs. the concept is that these units would be equipped with a closer range anti infantry soldiers that would provide excellent counter against shriek squads or stormy ambush teams. These units would be generally weaker in terms of heath and Armour than their ranger/airborne counterparts but when combined with armored support they would be dramatically more effective. Another feature of the mech infantry is to provide light AT by featuring a possible upgrade to a bazooka this would help protect allied Sherman tanks from enemy tanks attempting to flank them and give the allies additional AT capabilities.
Example Unit
Squad size: 5 men: 4 soldiers 1 sergeant
Un-upgraded equipment: 4 m1 carbines with increased fire-rate and higher damage but lower range and accuracy at medium to long range also sarg has a single Thompson SMG
Upgrades: Frag Grenades (2 Uses), Thompson SMG (4) Bazooka (1), and Veteran Sergeant.
Doctrine Upgrades can include
Anti Tank Team (Unlocks second bazooka)
Spearhead (extra suppression resistance and unlocks a sprint ability NOT FIREUP)
Bonuses From Tanks (only gained by proximity to your tanks not teammates also works for HTs)
1. Very high suppression resistance
2. faster fire rate
3. Reduced damage
4. Faster Movement
5. lower received accuracy
Squad has Brit LT fallow ability witch is only usable on tanks (not light vehicles)
This unit would add flavor to the Armour doctrine wile giving the unique armored capabilities.
Link to original Idea
http://www.omgmod.com/index.php?topic=743.0