I don't approve of air/wind or wood Logia ideas. Wood is such a varied material it opens up a whole new world of Logia to even consider, and air/wind was something Caesar could most likely accomplish.
I have a bunch of Devil Fruits of my own creation. Around a year ago I had come up with Buffalo's ability in extreme resemblance long before his introduction. I won't share them all here, but I'll tell you about some of my Logias. Just so you know in order for me to accept some of my elements I had to make my own classification that I refer to as Cross Logia. Cross Logia are Logias that are an element created by two elements, and can only take place in tangent. They cannot use the elements separately. Only together. I'll note when I'm referring to a Cross Logia.
Soil-Soil Fruit: Allows the user to into soil, but the consistency is such that the manipulation of it is limited to the users physical motions, which makes it one of the most unmaneuverable Logias there is. The true gift of this ability comes in its ability to nourish plants. The user can place seeds in themselves and manipulate the growth of the resulting plants. I favor imagining this as a female Logia, adding to the mother nature inspiration of it. This was my alternative to a wood Logia.
Ash-Ash Fruit: The user can burn themselves to ash, with or without embers. The user cannot generate more ash from themselves, but they can burn things to create more ash, which is a big part of what makes this Logia unique. They can send a burning wave along things that is like a cigarette burning at a highly accelerated rate, depending on the density and nature of the material. Humans are more resistant due to our fleshy bodies, though he can cause burns to them. The sustainability of the burn is up to the user, which is part of what makes this so dangerous. Spreading and sticking to things.
Sap-Sap Fruit: The user can turn themselves into sap, either as the sticky syrup or amber. This ability might not sound so bad, and maybe similar to that of the Candy Logia of that filler movie, but it distinguishes itself a lot. It was my alternative to a glue based ability. The user can create a web of sticky sap and move throughout it. They can create a snowballing effect with by turning into a ball or sending one out. They can stick to something and use it to attack. They can create sturdy forms with their amber state. They can close wounds made by Haki with sap or close the wounds of others with it as well. They can capture things within their sap body. I like the potential of this ability a lot.
Glass-Glass Fruit: A Cross Logia, the result of sand and lightning. The user can forge glass. I think the applications of this one are really straight-forward, and I'd like to just let others imaginations explore it.
Clay-Clay Fruit: A Cross Logia, the result of sand and swamp. The user can generate clay in both dry or wet states, but never so dry or wet that it becomes one of its two elements. It's makes their form very solid, but their ability to create ceramics makes them a weapons master of sorts, and they can create dolls and control them.
Sol-Sol Fruit: A Cross Logia, the result of fire and light. It is a light that has an aura of flame. This aura can be expanded by mid-frequency release of light waves, creating a solar wind like effect. A burning wave shown only by the almost see through fire expanding from the glowing body. This ability is devastating. The user is essentially unreachable. The user struggles to expand on its form though, the light becoming harder to sustain once in motion. The user can however release self-sustaining orbs of light that have their own fire aura. These can burn through everything they come into contact with, only stopping once expending their entire density. Granting enormous burning and penetrating power.
