Just to make this as clear as possible.
As was said before, you can take only one liquifier in the mentioned unit and you have to take this one with the Haemi.
If you took 5 Wracks and a Haemi you could take two and if you took 10 Wracks and a Haemi you could take three.
When the Codex mentiones 'for every X' it means for every completed X, not per X or part thereof.
This comes into effect, because the Haemi is an Independent Character and so becomes a part of the unit of Wracks the moment, they are deployed together. So before they are just 4 Models and can't take a liquifier. After, they were elligible, but it's to late to add one.
I must rule with eye and claw — as the hawk among lesser birds.