On page 163 of the core rulebook it mentions that artificer armour may have special features, but then doesn't give any rules for them. So I thought I'd write some up.

Roll once on the following table. If an artificer suit has a special feature then it only receives one roll on table 5-12 Power Armour History.

This is actually pretty brilliant.

There are good ones and bad ones - for example, I like the idea of hexagrammic wards a lot, but permanently adding a Narthecium to an armour, regardless of the wearer's Speciality, is a bit too much - not to mention +50 on the suit's Medicae? Added to what? Does the PA's Machine Spirit possess a full profile, Intelligence score included? If not, and the bonus is for the wearer, a Marine in this suit heals himself (and others) definitely quicker, and possibly more effectively than a trained Apothecary.

I'm not defending "game balance" or anything, but all in all, I'd rather go with rolling twice on the PA History (and possibly re-fluffing the results), because with the Core and RoB PA History tables there's a multitude of options to choose from, and the bonuses suggested here are a bit too powerful - and quite unevenly written.

There are good ones and bad ones - for example, I like the idea of hexagrammic wards a lot, but permanently adding a Narthecium to an armour, regardless of the wearer's Speciality, is a bit too much - not to mention +50 on the suit's Medicae? Added to what? Does the PA's Machine Spirit possess a full profile, Intelligence score included? If not, and the bonus is for the wearer, a Marine in this suit heals himself (and others) definitely quicker, and possibly more effectively than a trained Apothecary.

I'm not defending "game balance" or anything, but all in all, I'd rather go with rolling twice on the PA History (and possibly re-fluffing the results), because with the Core and RoB PA History tables there's a multitude of options to choose from, and the bonuses suggested here are a bit too powerful - and quite unevenly written.

I think the Narthecium only applies to the one wearing the suit.

I think the medi system is too powerful however, I'd add the Regenerate (2) with no toughness test needed to activate.

The first one is extremely powerful per fluff, but mechanically it works pretty good.

Only Grey Knights and the ordo Malleus know what Hexagrammatic warding is

The Machine Spirit taking control of the suit sounds pretty friggin cool

as for the augur array, I'd change the name to Advanced Targeting Systems, give a +5 to BS and WS, and add +1 pen to weapons since you're able to target with greater efficiency. Just my two cents

The Armour of the Remorseless Crusader, the Black Templar Relic from the main book, also lists hexagrammic wards in its description. I imagine that there is some knowledge of them among the Astartes, but much less extensive than the Ordo Malleus and Grey Knights.

Onboard Medicae is a bit overpowered, yeah. It's basically Regeneration, and the fact that it functions continuously bypasses one of the main limitations of medicae, i.e. that you generally take damage from several sources before you can be treated, and one check "treats" all damage you currently have.
Overall, most of these lean powerful, but that's the only one that's utterly broken. I'd say replace it with Regeneration that can function for X number of turns per day. I love regeneration mechanics, but true regeneration on a PC removes a lot of the narrative tension, as anything that doesn't kill you is rendered utterly trivial the moment combat ends.

Onboard Medicae is a bit overpowered, yeah. It's basically Regeneration, and the fact that it functions continuously bypasses one of the main limitations of medicae, i.e. that you generally take damage from several sources before you can be treated, and one check "treats" all damage you currently have.

Overall, most of these lean powerful, but that's the only one that's utterly broken. I'd say replace it with Regeneration that can function for X number of turns per day. I love regeneration mechanics, but true regeneration on a PC removes a lot of the narrative tension, as anything that doesn't kill you is rendered utterly trivial the moment combat ends.

I'd just make it so that in-combat it only applies once to each injury, and significantly boosts healing speed out of combat, but not to the point that Regeneration does. Perhaps natural healing triggers every 6 hours instead of every 24, while wearing the armor - or even every hour. Always treated as being Lightly Wounded for the purposes of natural healing while wearing the armor.

Mechanically what you propose is sound, but fluff-wise, this whole idea is a bit of a stretch for me - I mean, the Marines' prodigiously rapid healing rate is, for the most part, the result of their superior physiology, not the medical field technology they possess. I simply don't see how an artificer armour, however well made, could enhance the body's regenerative functions so much better than a trained Apothecary and an equipped medical bay.

Mechanically what you propose is sound, but fluff-wise, this whole idea is a bit of a stretch for me - I mean, the Marines' prodigiously rapid healing rate is, for the most part, the result of their superior physiology, not the medical field technology they possess. I simply don't see how an artificer armour, however well made, could enhance the body's regenerative functions so much better than a trained Apothecary and an equipped medical bay.

I agree and think the medicae skill that can act on its own is a bit too much. It makes an apothecary a waste of time.

As an alternative, a techmarine in artificer armour can also have a servo harness with a medicae arm. I believe the medicae arm can be found in Only War (somewhere else?) and there is a conversion table for scarcity to requisition somewhere- Rites of Battle or DW corebook, IIRC. Couple that with the "gene-seed anomaly" deed allowing one to be trained in medicae and you have a pretty good set-up.