noI like peasant militia it is a a very hard trip in the early game but if properly managed it becomes very powerful by mid game, unfortunately those poor bastards do not fare that well in the late game, you need more high end equipment and the guys using it have mediocre stats. That out of the way peasant militia won't be a fabulous end game party but it is a fun ride, that cripple crossbow specialist is priceless, lol.
actually peasant militia is the strongest origin in the game for the purposes of theoretical maximum power by a long shot
some lowborn origins are very viable in late game comps and having such a large number of potential units on the field + in the reserve allows for unmatched tactical flexibility which can trivialise even the hardest encounters
I disagree, on the tactical flexibility and the faith you put in larger numbers.
Fielding 16 guys is going to leave you both without space to manoeuvre and the fact that they are mediocre compared to a better background brother of the same level means most of your guys will shoe-horned into non demanding roles -> tanks, ranged, two handers and 2nd line two handers. Actually you will have trouble finding good archers and melee two handers, those roles and the lack of space will have you playing basically as an undead phalanx with some ranged attack added in. Once brothers start specializing in a weapon type you will have the option to use ones or the others but the basic tactic won't change, you will form a line and exchange attacks with the enemy using your superior numbers and two lines of effective brothers to weather them down until they are no more, you will roll over the enemy line but be unable to breach it and go through to attack back-liners such as enemy archer, necros... This tactic is all well, but once you find yourself against end game, with heavy spike damage and/or aoe damage this tactic is going to become less and less useful:
Against Schrats your second liners will be the perfect target for their aoe
Against Lindwurms your superior numbers won't be applicable unless you put many brothers in the aoe
Against southerners your packed lines are the perfect target for bombs and handgoons
Against legendary locations where you usually have a singular enemy you need to take out asap you brother will have trouble opening a gap to reach him.
For all those things you need the best brothers who can tank and aoe mob alone or when it is the moment surround the monster and destroy it before it can attack back, bad luck with peasant militia.
But it is worse if you need to push forward to create a hole in the enemy line and push into it to reach strategic targets in the back of the enemy formation, the poor ranged brothers don't help at this either.
TLDR: Superior numbers are great mid game but by end game it's a liability in the form of more AOE damage received, also your line will be less manoeuvrable and tactically unflexible.