The standard once dismounted is the the LAV Capt and Sgts fight the Vehicles, do a large degree they also managed the advance with most Pl Comd staying in th back on the advance, avoids the confusion of getting out of the turret under contact. Having never been deployed via RCN Boat, or Truck for an operation I frankly can't say, although I would imagine they would just slot into their respective organization as extra HQ elements. During my couple air mobile operations on Ex, the Helos dropped off the dismounts to seize vital ground while the LAVs punched through to them as "cavalry" - under the command of the Limas.
In reference to your comments about the "big targets" of IFV born infantry, I see your argument, but in todays battle field with mass proliferation of IR and II optics, your infantry platoon is a target regardless. I would rather be vulnerable to a BTR companies 3 m111 stands than every single one of their MGs as I advance to their position for example. Of course your vulnerable to tanks, but that's what your tanks are for.
The Estonian exercise is interesting, but a lot of the Baltic countries are doing things "in extremis" not in ideal. Absolutely stuff we should look at, but if we're trying to set goals for organization maybe no out best goal post. (I am however a big fan of the Latvian Spike teams rolling around in little ATVs)
Lastly, I don't know that anyone was dismounting the .50 of the M1113 under contact. In the defense sure, but not on the attack, and to try an equate the capability of an m1113's .50 to a LAV turret in terms of direct fires is... well it's apples and oranges in the extreme.
(apologies for the late reply, I was lost in the woods of Gagetown with OCdts)