The mistake you are making here is that you keep on clinging to the force of nature aspect of being a Logia. Check the SBS quotes above, Oda didn't say that a Logia is a force of nature, but simply some kind of aspect of nature. Mucus fits the criteria of being an aspect of nature. The fact that mucus is created by plants and animals does not make them odd ones out. Does this make them different from fire, magma, smoke, light, lightning, ice, etc.? Yes. But magma, smoke and ice are also different from lightning, fire and light. Does that mean that the former group's legitimacy as Logia powers should be brought into question? Or the latter? No. Dividing mucus from the other Logias does not make it an ¨odd one out¨ because you can further divide the remnants from each other.
Aspect of nature? Then why did Oda choose to make Doku Doku, Gomu Gomu, Kage Kage, Nikyu Nikyu, Horo Horo, Gura Gura and Ishi Ishi no Mi's (AND Jozu's, Isshou's and Kidds Devil Fruits) Logias? They're all aspects of Nature, in fact all Devil Fruits are an aspect of Nature in the One Piece universe.
What is it that the Logias have that they don't? Force of Nature or Elemental status. I'm clinging to this because you cannot refute it and have failed to, consistently.
Your argument here is invalid as all Logias are different whether it's Smoke, Magma, Lightning or whatever. What makes them the same type of Devil Fruit is what they can create and become, elements and forces of nature (as perceived by Ancients).
I could divide all the Logia abilities in this format:
Forms of energy:
-Light
-Electricity
Natural biotic materials:
-Mucus
Natural abiotic materials:
-Swamp
-Ice
-Magma
-Gas
-Smoke
-Fire
-Sand
And yet they're all forces of nature/elements except from the bolded one.
If mucus encompassing a large amount of materials makes it abnormal, then so does the Gas Gas Fruit, as gas can be any of the 118 elements that we currently know of in gaseous form. This is evident by the fact that Caesar can make poisonous gases, exploding gases, light gases, dense gases and even specify that he's affecting oxygen. If you want to count the Beta Beta no Mi as an abnormal Logia for this reason, then you must do so with Caesar's fruit as well, which would contradict what you've said before.
You clearly didn't understand what I was saying, so I simply wish to elaborate: Fundamentally, all Gases have free particles that will all fill a container, they have abstract shape. This is similar to say Magma (which is all superheated ash and rock), smoke (all a biproduct of a fire), fire (all oxygen + ignition to an object) etc. However, Mucus (like Wax and Poison) isn't all fundamentally the same. Mucus comes in many forms from living slimes to adhesives to snot to sap, all of which are very different, perhaps only sharing one thing in common, they're sticky. That's it.
Baby 5 is a Paramecia because what she creates and turns into is not a part of nature. This means nothing for the Beta Beta no Mi's legitimacy as a natural Logia.
However, people could say metal is a part of nature and technically Baby 5 creates and become different metallic objects. This is where things become blurred and the differences between these types of Paramecia and Logias become less defined. One of the reasons for such a debate.
Mucus not changing color when transformed also isn't odd because Caesar has shown the same thing.
Transformed into gas:
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Not transformed into gas:
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It's because of partial transformations. There's also the fact that Trebol's mucus is the same color as his jacket already :| So of course the color won't change much when he transforms.
Caesar can however, do this:
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Which is his genuine element form. The mucus carries the stripes and circles and markings from his jacket anywhere and everywhere. If he makes a rope, it's marked with the same markings as his clothing rather than looking like normal slime (which is not what you would normally expect from a Logia). It's similar to Crocodiles sand being the same colour as his clothes, carrying weird stripes and fur around, or Enels lightning being a pale colour, and having nipples should he launch a "thunder beast", or Smokers smoke having abs and the pattern of his cigars forever in the colourscheme of his smoke.