WITHOUT shutting your whole opinion down...
HPL2 doesn't support multiplayer, therefore, it is impossible to make a multiplayer version.
Furthermore:
- Amnesia's application does not ever connect to a server to access online multiplayer.
- It would be quite a hassle to get two people to use a keyboard and/or gamepad, either each or by itself.
- As you pointed out, Daniel is in fact, invisible, minus his left hand, and is not programmed for otherwise visibility.
- I wouldn't a large number to jump in on a multiplayer CS, given the methods of attempting.
- And I would rather play Amnesia myself to be immersed myself, not muck around with a/any friend I may want to play with, given immaturity possible when I come around a corner and he would toss a box at me.