So, I have a little quandary for people who play Tech-Priests, and those who GM a group that has one or more. Your average Tech-Priest is a Human who longs to become more than that, and grow closer to the Omnissiah (possibly a C'Tan, but not the point here). In an effort to emulate their god, many member of the AdMech swap out body parts for prosthetic replacements, escaping the weakness of soft flesh for the security of cold steel. So, here's the question; How do you prevent your Tech-Priest from constantly requesting more cybernetics? Even if you aren't belabored by the The Flesh is Weak talent (HotE, p.104), an ability I am personally VERY happy they included, but can see how it can get dicey, there is no reason for the TP to NOT request bits, nor for his or her fellows to not, at least initially, want to assist their fellow AdMech in ascending. Other than surgery and recovery time, I don't see a great hold there, to stop the Tech-Priest from just becoming a robot.

On a pointless side note, is there a maximum amount of cybernetics a Human body can support? I don't remember reading one in FFG products beyond mechadendrites, and Tech Priests and Iron Hands Space Marines do long to replace as much as possible, but I don't know if they can get to 1/5 of your brain, cradled inside a metallic shell, or if, at some point, the body says "no more", like in sci-fi games of my past (Alternity and Shadowrun come to mind). I've read stuff about ancient Tech-Priests who seem completely made of metal, but I don't know if it's really doable, even ignoring the irritation to the game it might become.

I am afraid I can't really help you with your core request, "How do you prevent your Tech-Priest from constantly requesting more cybernetics?" , but I simply must ask: why would you ?

In Only War, the availability of bionics might be greatly restricted due to a number of factors, and he'd probably have to argue with his own Adeptus Mechanicus hierarchy, and, seeing how he's just a lowly Enginseer (unless you've ruled otherwise), most of the fancy stuff would likely be out of his reach. Unlike even a generalized Tech-Priest that is part of an Acolyte Cell (Dark Heresy), he can't exactly use contacts and lack a lot of freedom to simply find and purchase said equipment, because he's attached to a Regiment and firmly entrenched in a hierarchy, both the military (Imperial Guard) and his own (Adeptus Mechanicus).

But overall, depending a bit on the player, circumstance and roleplaying, it is entirely in-character for him to strive for an ever-higher number of bionics and implants. In the field, however, the surgery and recovery time might be a really big issue, aside from the aforementioned availability and hierarchical restrictions or lack of sanction.

I know that if I ever get to play the AdMech character I want to play, preferably in a Rogue Trader campaign in a more generalized ruleset based on Only War, I'm going to be all about acquiring Best-craftsmanship bionics, and practically nothing more, in an attempt to embody the Omnissiah myself.

And as a follow-up to my previous question, based on the end of your post, why might it become an irritation?

As far as I know, there is no limitation whatsoever on the amount of bionics a person might have, other than the fact that some are obviously incompatible for various reasons (you can only switch out your arms and legs once, after all). Many a Magos have been depicted as being little more than entirely robotic or bionic, with probably very little of the original Tech-Priest remaining. Some even switch out half their brain, and in the end, all that remain of the old human might be half a brain and a spinal column.

As far as I know, there is no limitation whatsoever on the amount of bionics a person might have, other than the fact that some are obviously incompatible for various reasons (you can only switch out your arms and legs once, after all). Many a Magos have been depicted as being little more than entirely robotic or bionic, with probably very little of the original Tech-Priest remaining. Some even switch out half their brain, and in the end, all that remain of the old human might be half a brain and a spinal column.

Agreed. There is no setting or game mechanics reason that a Tech-Priest couldn't become almost entirely mechanical.

As for reasons for a Tech-Priest not to constantly request cybernetics, I can only think of one: time. Recovering from surgery and learning how to incorporate new cybernetics takes time and the Tech-Priest does have duties she must perform and missions to go on. From a pure gaming standpoint, you can always say: "Sure, you can requisition a new cyber-leg. Of course, you will have to sit out this adventure while your character recovers from the surgery. Why don't you go get the rest of us some pizza while we play."

I think I read somewhere that Flesh Is Weak (X) is limited to the TB of the recipient (perhaps the Black Crusade Core Rules). So a Tech-Priest with TB 3 would max out at Flesh Is Weak (3). Personally, I would limit cybernetics/bionics with this mechanic, as well. So the Tech-Priest (previous) could have 3 cybernetic/bionic implants/replacements (including mechadendrites) and Flesh Is Weak (3). To go beyond the limitations of TB you could use the Machinator Array (and any Rank prerequisites) as found in The Inquisitor's Handbook under Mechanicus Secutor Alternate Rank.

Remember, there are Location-specific TB bonuses from bionics/cybernetics, Flesh Is Weak stacks with Armour AP, Armour Monger increases AP...

I think I read somewhere that Flesh Is Weak (X) is limited to the TB of the recipient (perhaps the Black Crusade Core Rules). So a Tech-Priest with TB 3 would max out at Flesh Is Weak (3). Personally, I would limit cybernetics/bionics with this mechanic, as well. So the Tech-Priest (previous) could have 3 cybernetic/bionic implants/replacements (including mechadendrites) and Flesh Is Weak (3). To go beyond the limitations of TB you could use the Machinator Array (and any Rank prerequisites) as found in The Inquisitor's Handbook under Mechanicus Secutor Alternate Rank.

Remember, there are Location-specific TB bonuses from bionics/cybernetics, Flesh Is Weak stacks with Armour AP, Armour Monger increases AP...

Since so many of these games aren't quite as cross-courteous they claim/we might like, I'm leery to use much from BC. In HotE, they get Machine (X), where X equals the number of cybernetics, etc. That is really all the more limiting it is. In fact, without requiring Mech Implants, one MIGHT even argue that a run of the mill grunt, if they had enough techbits and training, could get this, rather than just important Tech Priests.

I don't see The Flesh is Weak in my BC corebook, though I might've simply missed it, and in other books, it is usually a "take it repeatedly" Talent, so rather very different. The TB would seem fair, but as they become less flesh, they become more inured to pain and damage, so I can see that max being less relevant as the number increases.

Have them make logistics rolls. A techpriest can get lots of incidental and minor buffs, but when things that have decent AP start showing up they're just as vulnerable as the rest of the party. If you think he's had too many, just say that there isn't enough Admech support at the moment to take care of all of his requests.

I'm not a fan of forcefully blocking a person's build unless it's genuinely detracting from other people's fun (unless they're getting outclassed because they have crapp builds, like a weapon specialist with no weapon skills).