Seriously, I have no idea. I want to know how would other people rule this feature because it is relatively difficult to pin down.
The feature is split into three sub features,
(1) That armour now counts as separate items for the purposes of your infuse items feature: armour (the chest piece), boots, helmet and the armour's special weapon. (2) Each of those items can bear one of your infusions, and the infusions transfer over if you change your armour's model with the armour model feature. (3) In addition, the maximum number of items you can infuse increases by two, but those infusions must be part of your arcane armour.
Sub features two and three are relatively unambiguous but sub feature one is a bit strange. My first assumption was that you could infuse a suit of armour like that anyway but this feature says otherwise so I drew up some ideas for how this feature may actually benefit an artificer.
1) The one that is probably correct. The arcane armour is treated as a single item for the purposes of infusing it. So you can choose whether to infuse it as a helmet, suit of armour, weapon or pair of boots until you gain this feature
2) The arcane armour is considered magical and therefore could not be infused until gaining this feature
3) Sub feature one is actually flavour and you could do this anyway
4) A mixture of the above, but if your arcane armour is based off of magical armour, you can treat the magical armour as taking up the chest piece and infuse the weapon, boots and helmet separately once you gain this feature
As to say, I don't know how to rule this feature so I mostly want to know how you would
Seriously, I have no idea. I want to know how would other people rule this feature because it is relatively difficult to pin down.
The feature is split into three sub features,
(1) That armour now counts as separate items for the purposes of your infuse items feature: armour (the chest piece), boots, helmet and the armour's special weapon. (2) Each of those items can bear one of your infusions, and the infusions transfer over if you change your armour's model with the armour model feature. (3) In addition, the maximum number of items you can infuse increases by two, but those infusions must be part of your arcane armour.
Sub features two and three are relatively unambiguous but sub feature one is a bit strange. My first assumption was that you could infuse a suit of armour like that anyway but this feature says otherwise so I drew up some ideas for how this feature may actually benefit an artificer.
1) The one that is probably correct. The arcane armour is treated as a single item for the purposes of infusing it. So you can choose whether to infuse it as a helmet, suit of armour, weapon or pair of boots until you gain this feature
2) The arcane armour is considered magical and therefore could not be infused until gaining this feature
3) Sub feature one is actually flavour and you could do this anyway
4) A mixture of the above, but if your arcane armour is based off of magical armour, you can treat the magical armour as taking up the chest piece and infuse the weapon, boots and helmet separately once you gain this feature
As to say, I don't know how to rule this feature so I mostly want to know how you would
Basically #1, except it only counted as armor.
What DxJxC said