I'll also believe that FMA grappling may not be as technically diverse or sophisticated as the ground tactics of BJJ. They're a lot simpler in "depth".
But then again "simple" does not necessarily mean "simplistic". Lets consider the historical development of battlefield-evolved arts; Japanese jujitsu for example evolved from the tactics of
yoroi kumi-uchi (wrestling or grappling in armor). This link offers more info -
http://www.humankinetics.com/products/showexcerpt.cfm?excerpt_id=3263
The likely tactics that would be favored would be -
1. To induce "kuzushi" or imbalance to topple an armored opponent. Really hard to get up with all that weight. Think also of the universal principle of "disrupting the tripod/triangle stance" of all grappling arts from the steppes of Mongolia to the English and Welsh shires.
2. To quickly and efficiently inflict "structural damage" kind of injury (i.e. - bone breaking) putting the opponent out of the fight.
Defanging the snake?
3. Quickly transitioning or re-acquiring weapons and moving to the next target/attacker. Really needed if you're fighting multiples in quick skirmishes or need to complete your objective (this was the military of course). This is why you don't go to the ground if you can help it or GTFU should you find yourself there.
All techniques then would be built around and maximized for these specific tactics, enriched by time, variations, fresh ideas, etc. However, they all began from "simple" foundational tactics.
Aside from "dumog" a friend of mine happens to be a native of the Cordilleras, home to the mountain peoples of Northern Philippines (Igorots, Ibalois, Kankanaeys, etc.) He tells of their native style of wrestling called "bultong". Before it became a ceremonial practice of settling disputes in recent times, in the past he says it was grappling with a twist - it was practiced in such a way that it supposes that a fighter had a hidden weapon, like a small blade. Admittedly though, I haven't seen this yet.
