A few contributions:
First, the Xenomorph template seems to only grant a tail attack, but both in the movies and in the games Xenomorph's made from humans seem to also be able to attack with their claws, even though humans obviously don't have claws. I'd suggest granting a claw attack based on size & progressing the claw damage by 1 dice if the host already had a claw attack.
Second, to my knowledge, a xenomorph has never infected Vermin or anything resembling Vermin in the series. I think it's kind of weird that the template can be applied to Vermin.
Acid Immunity may be appropriate, since they basically have acid for blood.