MC Lifetime Tracking

Non proper syntax / name for 1.12
For 1 target pigman being alive at a time (probably can be improved for multiple simultaneous but don't have time for that)

initial setup
	scoreboard objective "counter" + setdisplay belowName
	scoreboard tag "tracked" + tag the alarm pigmans with it

cmd block - timer (anywhere around the farm)
	(repeat) execute @e[type = pigman, r = 100, tag != "tracked"] summon armorstand ~ ~ ~
	(chain) execute @e[type = pigman, r = 100, tag != "tracked"] scoreboard @e[type = armorstand, tag != "tracked"] "counter" + 1

cmd block - resetter (at death pos with pressure plate)
	(impulse) scoreboard @e[type = armorstand, tag != "tracked"] tag armorstand with "tracked"

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Ideas for improvement
if you can compare an entity's score directly with another entity's score in the selector (which idk if you can in 1.12)

(repeat + chain)
use another scoreboard objective "id" for both armorstand and pigman
all pigman not tagged will summon new armorstand + any other 1 time behavior upon spawning (eg place button to prevent repeats)
all armorstand will add 1 to "id" for pigman/armorstand not tagged
all pigman/armorstand gets tagged
all pigman add 1 to "counter" on armorstand with same "id" score