Now that we've addressed the basics and the three major archetypes of magic-users, we're going to start talking about specific types of magic-users.
A Tattooed Man is, as described in RIFTS Atlantis, a humanoid individual who augments his extensive martial training regiment and practice with a large array of power-generating tattoos. Within the environment of RIFTS Earth, and in much of the Megaverse, Tattooed Men are presumed (correctly) to be a caste of slave warriors for one of the Splugorth species of Sufficiently Advanced Aliens- and otherwise to be scions of one of the Atlantean houses long dispossessed of their Earth homeworld. This is not always the case, and below I shall describe one way that a Game Master may reinterpret this specific form of magic-user for his own campaign. I will also address the major error in terms of game mechanics, and provide one solution that better fits what the powers of a Tattooed Man. While the game makes distinctions between various Occupations that fit this description, I will--for the purpose of this article--lump them together.
Notes on the Occupational Culture
The culture of Tattooed Men varies upon how the power-imbuing process goes for them, but there are common elements. The slave-warriors produced by the Splugorth in industrial quantities experience severe physical trauma due to the tattoo masters there not caring about the recipient's health or sanity; those that fail to endure the process are dispatched and have their corpses fed to other slaves. Those created by the Atlantean houses express far greater care, as their Tattooed Men are often treated as elite warriors and therefore enjoy higher value in the eyes of those creating them- manifesting in both longer times taken to imbue the tattoo powers as well as more comprehensive care taken in both preparation as well as recovery from the imbuing process. This formative, initiatory experience sticks with a Tattooed Man thereafter and becomes one of the defining experiences informing his character and identity. Because the process for becoming a Tattooed Man is, inherently, an initiatory one there is a certain commonality of perspective amongst Tattooed Men regardless of their relationship with others like them. It's not the same as that between Warlocks and the Elements, but rather the sort that often arises in real-world professional societies.
The fact that Tattoo Magic is known to be physically traumatic means that the process by which the tattoo master imbues the recipient with the power that the tattoo conveys is an amplification of the real-world tattoo process, which is not without discomfort if not outright pain willingly taken by the recipient. So, let us imagine that the Tattoo Magic technology takes that real-world tattoo process and uses it as a means to introduce a limited form of physiological retro-fitting of the body to accept the necessary infrastructure needed to wield the power that the tattoo imbues. This process, as one would expect, should be akin to receiving cybernetic or bionic augmentation (or, indeed, any other augmentation of the body; to get the same result, the process must also be the same). Taking this process slowly, as one would for any mundane form of major surgery (because that's the closest mundane equivalent), minimizes the impact to the recipient's physical and mental health. Going through it fast reliably damages both; imagine getting put under the knife while awake without anesthetic with upwards of a dozen procedures done in rapid succession or in parallel, and then patched up in a haphazard manner before being pushed out the door- that's the Splugorth way of doing things. If you're not taking this into account, you're doing the Tattooed Man wrong.
A Note on Tattoo Magic
In terms of how the game mechanics interpret their powers, I see this as a major flaw. The rules treat them as if they were just a hobbled spell-caster, when they have no such knowledge or ability whatsoever, and as a result it is difficult to avoid playing (as-written) a Tattooed Man as just another form of Fighter-Mage (or "Gish", to borrow yet another term of D&D-originated jargon). The visual depiction of Tattoo Magic reinforces this erroneous notion, when the mythological origins of Tattoo Magic are ignored instead of emphasized; Tattoo Magic should not result in an individual who looks like they ran with an outlaw biker gang for too long, or whored it up for Suicide Girls, but instead should resemble the Celts covered head-to-toe in woad with knotwork draw over their flesh or the warrior society tattoos found in many peoples present and past: specialized, integrated, highly-symbolic whole-body tattoo system networks that link the body's points of power together to fuel the powers granted by the tattoos. (Hell, your stereotypical Yakuza better fits the Tattooed Man than what Atlantis depicts.)
So, instead of spending mana as if a spell-caster, Tattoo Magic should work the way that Committed Charms do in Exalted: the player spends motes of mana to activate the effect, and until the player decides to end the effect the Tattooed Man cannot recover those spent motes. Furthermore, some of those powers that (as-written) require the use of a specific tattoo power to generate the effect should instead be made baseline to the Occupation's core powers (such as the Armor power; it should be presumed as part of the Tattooed Man's transformation from an ordinary mortal into a super-powered warrior). A power that discharges attacks upon a target should have an activation cost that follows this commitment scheme, which should itself be a nominal one, and a per-use cost thereafter. Tattoos that generate animated minions should have a high commitment, but no other costs, as the minion itself is sufficient to warrant the cost. (Which also means that there needs to be a significant revision to the tattoo powers.)
A Variant Example: Tolkeen
There is no doubt that the City-State of Tolkeen (especially my revision of it) would use Tattooed Men. However, the magical society there would not condone the usual Splugorth practice and neither would it tolerate the conservatism of the Atlantean procedure, not when there is an alternative that generates the faster production of the former while retaining the superior quality of the latter. As usual, the secret stems from the incredible store of mana that Tolkeen possesses coupled with the scientific and engineering know-how of the dominant magical society; having reverse-engineered Tattoo Magic from Atlantean and former slave Tattooed Men, Tolkeen figured out exactly how Tattoo Magic works and created an improved procedure that avoids the hassle and the risk. The drawback is that it requires the properties that, on RIFTS Earth, only exist in Tolkeen's Inner City.
The Tolkeen procedure work by taking the recipient into a facility wherein he is stripped naked from head to toe and then has his whole body scanned; this information appeared on the technician's screen, providing him with a complete DNA profile as well as real-time monitoring of all vital signs. At this point, the technician initiates the process; the recipient is told to visualize himself as if being armored up for the first time. (This is, for all intents and purposes, true.) The technician, under supervision, guides the recipient through the imbuing process via guided imagery; this allows for easier acceptance of the augmentations installed while minimizing any awareness of discomfort. The actual drawing of the tattoos is done by the supervisor, using the recipient's DNA and psychological profile to customize the symbolic imagery necessary for the tattoos to function properly, and he does so using a remote-operated robot.
Instead of using ink and a needle as the medium and tool of transmission, this is done directly through a laser transmitting the epigentic signals to the recipient DNA and directing the DNA expressions with the help of the recipient's mental state (hence the guided imagery). This completely avoids using the harsher processes that going through the body's cellular or grosser level of organization to achieve these results usually employs, achieving the same speedy results, and getting the recipient to aid in his reconstruction as it happens avoids the mental health issues entirely. Instead of taking days or weeks to finish, including recovery, Tolkeen's procedure takes hours; it's a full working day process, but the recipient is ready for action immediately afterword.
(Note: Tolkeen provides this procedure to anyone willing to commit to a period of reservist service in Tolkeen's militia lasting no less than five years; no other form of payment is accepted. Furthermore, Tolkeen's results tend to produce Tattooed Men whose aesthetic runs to Asimovian blends of high-technology and high-magic (e.g. Tron Legacy, Saint Seiya) than the Woad Warrior types.)