If you're OK with regenning, and only want to remove ambushes while leaving sieges intact, replace the goblin (civ)'s [BABYSNATCHER] and (creature)'s [INTELLIGENT] tags with [CAN_LEARN] and [CAN_CIV] in the creature RAW.
I'm going to try this, thanks for pointing it out. I did not know that this new version makes every underground game interesting, because I went back to the previous version and tried like 6 times to find a fun underground area and that's why I didnt want to regen.
Now that every game has this underground stuff I think I will restart, and this is more what I am looking for, to stop the annoying nonstop ambushes (4 at once in my current game, swords, crossbows,whips, and a bunch of slaves all at the same time) but keep the fun siege and invasions intact.
Also I did some creature testing in the arena and I see what you are saying about weapon types, iron vs iron doesnt do much damage, but once you go up a tier it slaughters the opponents. I had one goblin kill a dragon/cyclops/other beasts by himself just because he had steel. I'm going to focus on ironing up and like you said, equipping steel weapons to slice through their armor quick.
Although I have to say I think the equipment focus is nice, but too radical in its current implementation. One goblin in all iron vs 10 dwarves in all copper...goblin won without much effort, and the ganging up should account for massive damage IMO.