[@Kazemitsu][@Shoryu]

Okay, you guys raise some fair questions, and I'm going to address them.  The primary reason for considering the infection factor of the X to be so difficult a thing to overcome is largely due to the sheer plague-like quality that it has.  Worse, it's a thinking and adapting plague, so consider the way it acts as whenever you play a round of Plague Inc, about how you make the virus adapt around human measures to contain it.  Now, you guys do have a fair point in that there isn't really a case where the X come across a non-Metroid devouring species that has adaptation, and that it is TRUE that infection can take time.  One sample of X Parasite hitting Samus was clearly taking hours to fully infect her and her suit.  After they cut the suit away from her and used the Metroid-based antidote, it took hours more for the SA-X to become active.  The difference here is that you are away from support that can help you, and the Federation either cannot or will not do the same for you as they did for the Bounty Hunter.

The other point is that I am not really being strict about the creativity of a species, so that you can go a bit wild.  It's why I wouldn't actually care if you made a black-dragon-y guy, provided he could fit on ships and through corridors, because that's kind of a must in the situation.  That said, I'm going to make a ruling here and change my mind about the Zerg-like character, Kaz.  The X are still suppose to be this infectious horror that the Metroids were specifically the antithesis for, and that no other known species has the same qualities to combat them, but I'll let this guy go if you want him with just one condition: The X Parasites themselves do not fuel his adaptability, only the traits they were taking from other distinct creatures.  The X should be incompatible to the character's disgestion, and that the body would excrete them ASAP.  Part of the game and the plot is how they NEED a means to stop this menace, and that they don't exactly have it, so I can't give you perfect immunity.  Fair?