You are right.
auto pass the psychic test for force weapons and +1 attack for everyone in the unit sounds a good deal to me. Remember force weapons instant death works against any model with multiple wounds. Sure you can't use hammerhand as well, but if an attached
IC uses hammerhand thats conferred to the whole unit. If your
IC is a level two psyker then they can use hammerhand and activate their force weapon too.