Are the separate pieces from the Armorer Artificer's "Armor Modifications" still considered "A suit of armor" for infusions?

Question

The title is a little convoluted, so hopefully I can explain better here.

At 9th-level, an Armorer Artificer gets the class feature "Armor Modifications":

You learn how to use your artificer infusions to specially modify your Arcane Armor. That armor now counts as separate items for the purposes of your Infuse Items feature: armor (the chest piece), boots, helmet, and the armor’s special weapon. Each of those items can bear one of your infusions, and the infusions transfer over if you change your armor’s model with the Armor Model feature. In addition, the maximum number of items you can infuse at once increases by 2, but those extra items must be part of your Arcane Armor.

Effectively giving the Artificer three more things they can infuse.

Do the boots and helm count as "A suit of armor" for the sake of infusions?

For instance, the "Armor of Magical Strength" has a prerequisite of "A suit of armor". So if the armor was still considered one piece, you could infuse the armor. But now it's considered four pieces. Can I infuse "Armor of Magical Strength" on say, the boots portion. Or are they now only considered boots and can only be infused with "Boots of the Winding Path"? And the helm can only be infused with "Helm of Awareness"?

The follow up would be, if they are still armor, does that mean a character cannot infuse their special weapon as a weapon?

I found this question, which would suggest that the weapon because a weapon. I'm asking whether boots become boots or are still part of the suit.

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It just seems like a crappy feature to say, your armor is now four pieces so you can customize with more infusions. But two of those four can only be two specific infusions and both of them require attunement.

Although, an argument can be made for not only those two infusions, but use the "Replicate Magic Item" to infuse the boots as "Boots of Speed".

Answer 1

Only the “armor (the chest piece)” counts as armor for the purpose of infusions requiring armor.

The helmet is a helmet, the boots are boots, the special weapon is a simple weapon, and the chest piece is “armor”:

That armor now counts as separate items for the purposes of your Infuse Items feature: armor (the chest piece)

Further, any infusion requiring a “simple or martial weapon” can be infused into the armor’s special weapon, since each weapon is simple (melee or ranged) weapon.

The Replicate Magic Item infusions have numerous options for boots, helmet, and gauntlets.

Now, in the question you state:

But two of those four can only be two specific infusions and both of them require attunement.

However, there are numerous items on the Replicate Magic Item tables which can be applied to boots, headwear, and gauntlets, so the two infusions you mention are not the only infusions available for the boots and helmet, and there are numerous gauntlet infusions in addition to the infusions requiring a simple or martial weapon.

Answer 2

You still just have one "suit of armor"

The 4 "items" you can infuse are listed in the feature: armor, boots, helmet, and weapon. Only one of these is a suit of armor, so you can only use one infusion that requires "a suit of armor". Similarly, you can only use one boot infusion, one helm infusion, and weapon infusion, since the armor consists of exactly one of each of these.

(It's admittedly a bit confusing that the feature splits your suit of armor into 4 parts, one of which is itself considered a suit of armor. That's why the "armor" part is parenthetically described as "the chest piece", and it's also why the feature says "counts as" instead of "becomes" or something else.)

Your options are less limited than you think

As for the supposedly limited choices for infusions of the boots and helm, I count no less than 7 infusions available for the boots and 2 for the helm, though some only become available at 10th level (1 level after getting this feature). Admittedly, these all require attunement except for the Boots of Elvenkind. However, if I were a DM, I would also allow just about any headwear-based infusion to be put on the armor's helmet, such as a cap of water breathing or googles of night. There are numerous such infusions available, including several (like the two just mentioned) that don't require attunement. This is a minimal change to balance, since the artificer could simply acquire or craft the required item separately from the helmet and infuse it regardless.

Furthermore, the attunement requirement is less problematic than it might otherwise be once you get to 10th level, since you gain a 4th attunement slot. If it helps, think of this as a major class feature that comes partially online at level 9 and more fully online at level 10: the added attunement slot, additional infusions known, newly learnable infusions, and added infused item at level 10 all synergize well with Armor Modifications from level 9.