Would this work to allow you to put armor on your Eidolon and self at the same time or would it still be prohibited?
Or is the armor slot not prohibted, it just has a negative that is involved with it?
In either case would this feat allow non penaltied simultaneous armor use on an eidolon and it's summoner?
Extra Item Slot
You are able to wear magic items more easily than other creatures of your kind.
Prerequisites: Non-humanoid body shape.
Benefit: Choose one magic item slot not normally available to creatures with your shape. You can now use magic items in that slot.
Special: Feats that are meant for familiars can be switched out for a familiar's default feats (as listed in the familiar's statistics) if the familiar meets the prerequisites. Such feat replacements must be made when the PC first acquires a new familiar, and-like all new feats from supplemental sources-the new feats should be approved by the GM before being integrated into play.
Pathfinder's "magic item slots" refers to wondrous item slots.
This table would seem to contradict your statement as it clearly lists an 'armor' magic item slot.
The feat in no way bypasses the eidolons "An eidolon cannot wear armor of any kind, as the armor interferes with the summoner’s connection to the eidolon." bit of rules text.
I was also leaning heavily that way, just wanted to see if there were any compelling arguments from the other side.
The rules don't actually say what happens if you put armor on an eidolon. It's just an assumption that it would dismiss the eidolon. If it did, then the eidolon would have to be careful of someone putting a helmet on its head or draping some light chain over its back.