Allies Unknown is for most people playing with LW2 on a pseudo black list, listed as "tanking performance both in strategic and tactical layer" and this seems to be the case for some people. While some suffer none of this.

But if you dont want to deal with this, you can actually use this mod without it and everything works fine.

Allies Unknown also adds Grey Market and lets you recruit non-humans, if you are playing Mod Jam it even lets you recruit other aliens like faceless or mutons. But thats not really the intended way Kiruka expects you to get them.

You can boot out the Allies Unknown and 4. resistance faction slow and just roll with mod alone.
You just wont be able to legally get these unless you resort cheats.

By opening up the console, just type in this
AddViperSoldierRecruit

This adds one recruit to your barracks that functions as intended.

Though few notes when it comes to LWOTC

1) Vipers are not part of NCE, so they are by default better than your soldiers in most ways. All Vipers will start with 3 HP, 15 dodge, 5 defence and 65 aim so they are above average, they also have around 2-3x will when compared to LWOTC troops (base will was considerably lowered so fatigue and mental attacks are more dangerous)

Vipers also have better eyesight, this might be the most game breaking atributes they have because it lets them hit Advent when they cannot see them. So you can pull stunts like area supression on a hopeless pod in the open or always being able to make the first pick before they can scamper which just snowballs.

2) They dont have 3 utility slots, only 2, so they are much worse as grenadiers and other classes reliant on consumables. Feasibly because they start with only 3 HP you will always give them ablatitive armor so you only have 1 slot to work with.

3) Their maws are too expensive and cost as much as end game weapons and those are the starting ones.

10 alloys for acid maw ?! You could buy warden armor instead ! But i guess maws are just a cherry on top and you wont even need them.

4) Presence of this mod changes Advent vipers too, their binding can now fail and your soldiers can break free, i have no idea what Strenght is calculated from but its used for the dice roll if the victim breaks free.
So this nerfs Advent vipers

5) If you are playing with playable aliens, Frost Adders on XCOM side cause CTD if you try to rush and bind with them.

6) The ally tongue pull is free action and even gives mobility to those without any AP left, singlehandedly the most powerful free ability in the entire game with endless tactical potential.
Failed to melee enemy with shinobi ? Just pull him back !
Move for 1 AP and pull your most distant ally, skipping 2 AP worth of movement ? No problem !.