So my next special squad will be shield dwarves, dual wielding shields. I think those might work pretty well as, well, zerg rush front troopers, especially against archers.
While waiting for a second subject to grow up to form a sparring team, I've already set one dwarf wielding two nethercap shields (too bad they don't do cold damage) to do individual training sessions in a barracks.
What I've noticed, is that contrary to dwarves wielding a weapon and a shield, doing individual training sessions, a dual shield wielder actually trains shield skill, it even trains as fast as discipline. Just under two months of training, and both skills are already adequate! However, it does not gain any fighter skill. (A dwarf with weapon and shield doing individual training sessions trains weapon skill and fighter skill, not shield).
Possible implication: I think that civilians will be able to still do all jobs except ofcourse mining, woodcutting and hunting when dual wielding shields. It might very well be the very best possible defensive gear option for civvies, if you can manage to spare them a few months training session time to get some shield proficiency.
I'm curious which skills will be trained best when sparring (except ofcourse shield). Will they focus on wrestling? Shield bashing? We'll see. Depending on the focus, I might switch to a heavier material shield.