Space Crusade Librarians

A Librarian would usually be too unstable to command a tactical squad, they would be a powerful Marine with an impressive Psychic ability. But the psychic ability should be simple to keep track of.
So:

Stats and Weapons:
The Psychic miniature will have a big sword or stick, and maybe a gun, so we can arm him as a Commander with 1 life point. Maybe bolt pistol + power axe, or power glove + power sword. That makes him a sort of Hand to Hand heavy weapon, with normal movement of 6.

Psychic Abilities:
A simple rule would be that the Librarian can take control of any 2 Alien events, attacking the Alien instead of the Marines, at the cost of one Equipment card. Or 2 Alien events at the cost of 2 Equipment cards.

More complicated:
There are 5 spells, which backfire frequently.

Psychic power #1 "Smite": Instead of attacking, the Librarian may roll 2 red die, attacking all revealed aliens within 2 squares (even out of LOS, diagonally OK). If the total is 0, the Warp overcomes him, his turn ends, and he misses the next turn.

Psychic power #2 "Jinx": Instead of attacking, the Librarian may roll a red die. A 1, 2 or 3 causes all Androids and Dreadnoughts within 5 squares (even out of LOS, diagonally OK) to miss their turn. If the total is 0, the Warp overcomes him, his turn ends, and he misses the next turn.

Psychic power #3 "Teleport": Instead of attacking, the Librarian may roll a red die. A 1, 2 or 3 instantly moves him up to 12 squares (even out of LOS, diagonally OK). If the total is 0, the Warp overcomes him, his turn ends, and he misses the next turn.

Psychic power #4 "Time Warp": Instead of attacking, the Librarian may roll a red die. A 1, 2 or 3 allows all Friendly Miniatures on the Librarian's board section to take a second turn immediately (not the Librarian). If the total is 0, the Warp overcomes him, his turn ends, and he misses the next two turns.

Psychic power #5 "Control": Instead of attacking, the Librarian may roll a red die. If the result is  0, he may take control of any revealed Alien he chooses (even out of LOS) for 1 turn. If the result is 1, 2 or 3 the Warp overcomes him, his turn ends, and he misses the next two turns.

Missing a turn:  Any miniature missing a turn may not move or fire, he can defend in Hand to Hand, but if he wins it is a draw, if he loses he is dead.
Cost: If killed, the Alien gets 10 points for the Librarian, like a heavy weapon. He costs an equipment card to deploy.

Comment: So, the Librarian will make Orcs think twice about Hand to Hand, with only a 7% chance of killing a Power Sword and Glove Librarian. A Dreadnought has a 32% chance of killing him in Hand to Hand.
He can control a Dreadnought for a turn at the cost of missing 2 turns. The Alien will shoot him as soon as possible, so he will tend to hide around the corner. He is hard to kill with bolters, even if he is missing a turn. The Alien may keep the Dreadnought unrevealed or away from other Aliens if the Librarian is active. So the Librarian's influence will be felt across the entire ship.

Terminator Librarian: "Terminator Chaplain/Librarian" Equipment card: (Based on The Terminator Librarian in White Dwarf 134 with a Power Axe and Storm Bolter) armor is 3, 1 red + 1 white dice for firing, 2 red die + 2 white dice for hand to hand. He would also have the 5 spells.
An extra 5 points to the Alien player for every dead Terminator.
1990 style

Alien Librarian: The Alien Commander could be a Librarian, but we would call him a "Sorcerer". He would be a huge threat, worth 30 points. He has to be revealed to use spells.

Librarian Spell Cards
Instead of "miss a turn" you could print spell cards, you get any 2:
Librarian Spell Cards