Hypothetical scenario where blizzard wants to rework the Diablo 2 mercenaries in order to balance away from A2 merc hegemony
You are in charge of the Merc rework, what would you do?
It can be a targeted change to a specific merc or more global , bring your ideas in!
Give the A3 fire merc Enchant and start a Immolation zone 
I would remove all the current mercs and insert an npc in the cow level who sells mercs.
There you can choose what aura effect the merc would have, and you would have to pay for the mercs aura in runes, and the aura would only last for a week, then you would have to renew it.
I’d request some statistics about usage… and double it 
Or maybe replace them by a gold-collecting unicorn - haha
if you can’t buy a cow mercs , no deal for me.
imagine having a skin for act 2 merc to look like a cow and going “moo” at every attacks 
(joking but fun to imagine)
Maybe:
Act1 : more tanky, multishot, immolation arrow and big freezing arrow
Act3: enchant, blizzard, thunderstorm, more damage
Act5: low level shout and battle order
drop all the current mercs… and let people run around with cain…qual-kehk, akara… natalya … other npcs and merc captains lolol
watch out for butterflies if you are using cain though.
A POe’s righteous fire skill? A mixt between Blaze and holy fire?
Would be funny and justify its melee aspect
A1 more tanky, would be funny if they had Fade when struck
Would you keep A3 melee behaviour or make it full caster?
Mine would be the Act 1 Rouge. This Mercenary would have a different passive ability. Maybe something that allows her hire a bonus to attack speed as long as the character uses a bow. But it’s something that she has to cast, Like that aura she has.
I would just leave Act 2 alone, but improve the skill tiers for each of the others by difficulty.
Remove act 2 mercs, needed a break - but that’s not frozen, they might come back if you pray.
One funny thing I heard about rogue was to make her come with her own arrow quiver… a rare one that you can reroll or improve with gold like gambling
you just had to say that didnt you 
Meh. A2 merc is overrated. I prefer the A1 merc with the Edge, Harmony, Faith or Ice.
Make items brake on merc.
Act 1 merc: improve AI so she’s more aggressive in terms of acquiring a target and starting to shoot faster. If she gets meleed, run away. Give her increased movement speed and/or dodge/avoid/evade. Maybe buff the range of inner sight (possibly for Amazon’s also) now that we’re playing with different resolutions.
More controversial probably but: you could consider making Inner Sight show affected mobs on the map as well.
Act 3: AI improvements like mentioned for A1 merc.
Give fire one fire mastery and maybe warmth (just for the synergy bonus to inferno to buff the damage). Or swap inferno for fire wall or meteor. I could see giving them enchant as an option or maybe give them a resist fire aura (I wouldn’t want to give all mercs Pally auras baseline, but the specific ele resist auras would make sense for Act 3 mercs I think).
Give the cold one frost nova also and cast when there’s more enemies nearby. Have the AI prefer to only ice blast if there’s only one target, glacial if there’s more but out of range and frost nova if they’re near him. His theme is CC so it doesn’t really need to do much damage. Could give it frost resist aura if you want to give all 3 an aura to add something more.
The lightning one you could give static field so it was no longer a major sorc exclusive (have it cast on a cooldown if there’s something in range at higher health). If that was too good, give it thunderstorm and lightning mastery. Maybe energy shield as well and if they essentially have infinite mana then it would just be a DR for them. Lightning resistance aura if you decide to give them an aura.
Act 5 merc: give some with find item, some with battle cry or even the buff cries (just one so you’d have to choose which one you wanted). Could give them barb passives like Iron Skin and Natural Resistance.
Give them better AI.
Imagine giving A3 merc old skills like flame wave, elemental, lightning wave
Act3 merc is an iron wolf, so was the Diablo 1 sorcerer that’s why they dress the same
Would be funny that A1 inner sight reveals a part of the map haha
Finally on a5, I feel find item is too powerful of a perk on a merc, I’d rather have find potion, a merc is supposed to be assistance in combat, not a lucrative endeavour .