Personally, the only changes I would have made to the Rogue Marine advance would be to require that the implants be 'bought/activated' in the order they were implanted - so Unnatural Strength/Toughness would have to be the first implant related purchases, but separate from the various talents (so you could still get Bulging Biceps, but you couldn't buy the Betcher's Glands and spit acid before you bought the Larraman's Organ to stop blood loss.)