I'm a bit on a hurry, but I post the link to the mod blob and I begun.
It's far from finished, you can at least kill aliens in the vessel located on the world map (2nd island) and maybe try the new claw weapon. I don't know what else is exactly inside, don't know if it can be compiled, but the executable inside run fine.
Maybe it can be useful, maybe I'll finish it sometimes, but for now, here it is.
http://helltgivre.free.fr/ivan/Alien_Mod.zip