First off, I'll begin just by restating the basic stuff we all already know, just so it doesn't have to be said again, over and over.
The 3 types of Devil Fruit as we know them:
Paramecia: A fruit that makes some minor but fundamental changes to the users body that gives them their ability. (A good example would be the changes made to Buggy's body that allowed him to seperate himself at will, or Alvida's body that gave her that ludicrously smooth skin, neither of which change the user's body to an entirely different substance, which as you will see later is my principle point.)
Zoan: A fruit that creates a hybridization between the species that the user is originally and the species that the fruit specifies; they gain 3 basic forms that include the creature's original form, the creature's half-original half-"fruit based" species form, and the creature's full "fruit based" form. (Dalton, Rob Lucci, and Chopper are good examples of this, with Chopper obviously having altered his abilities using his creation: the Rumble Ball.)
Logia: A fruit that converts the user him/herself into a fundamental element such that their body becomes that element and they gain full control and usage of that element in whatever form they find it. (Luffy's brother Ace can convert himself entirely into fire, and then he can also spawn into a much larger mass of fire and manipulate that fire. Enel was lightning in much the same way that Ace was fire, and he could control that lightning and likely any lightning he encountered as he pleased. And finally Crocodile, bless his heart, was Sand which isn't a principle element like Fire or Lightning or Ice, which is why I can make my case in the first place. He could turn into sand and so on, but most importantly, he could control the sand around him that wasn't even part of his body, proving my statement about Logia users controlling stuff made of their element even if it isn't part of their body.)
Ok, now we don't have to repeat any of that in the discussion.
So here's the question. Luffy is listed as Paramecia. However, his whole body was changed into rubber, not an element but still a substance.
So if his whole body became an entirely different substance isn't he halfway between a Paramecia and a Logia fruit? All our other Paramecia users didn't have their entire body become a substance. They just had a change to the attributes of their bodies. And obviously Logia doesn't have to be primary elements like Fire and Ice and Lightning and so on. Because we have a Smoke user and a Sand user, neither of which fit into that category.
Regarding the first question I have another; where is it said that Luffy ate a Paramecia fruit? Could I get a link to that?