you can import enemys and entities etc. look at Everlone thread, he put a penumbra enemy as a download and it works
also download his level if you want some penumbra entities and wall and ceiling textures.
But yeah making ai is very very hard to do unless you've had training or spend alto of time learning... that could take a year before you can make decent ai if you spend good time on it.
Oh and it wouldnt be too difficult to give entities animations etc from amnesia enemys. Eg. this will sound rediculous but its an idea... give a box the animations and blah blah blah of the water lurker, then you will have a box chasing you in the water i assume. But you would probably need to get help with it unless you knwo what your doing.