Magellan and Mr.3 could both turn into their respective fruits. The key points Chou brought up (elsewhere) regarding Luffy is that he is solid AND he can't turn it off, so you're probably mostly on the ball regarding the permanence thing.
Yeah, though it seems normal logia can "liquify" better than Magellan, and we never saw if he could regenerate after taking a bullet through his body or stuff like that.
So just for fun...what Logia are left?
(chou please correct any japanese issues obv)
1.) Rock Rock (Iwa Iwa no Mi)
2.) Water Water (Mizu Mizu no Mi)
3.) Blood Blood (Chi Chi no Mi)
4.) Plant Plant (shokubutsu is what I'm getting but that's long lol)
5.) Air Air (Kuuki Kuuki no Mi)
6.) Wind Wind (combine 5 and 6 if too similar) (Kaze Kaze no Mi)
7.) Oil Oil (Sekiyu Sekiyu no Mi)
8.) Wood Wood (Moku Moku no Mi, from mokuton)
9.) Cloud Cloud (Kumo Kumo no Mi)
10.) Metal Metal (I was getting Kane, but I thought that was more bell, so tetsu tetsu? I know that is iron or steel though)
11.) Steam Steam (Jouki Jouki no Mi)
12.) Clay Clay (Nendo Nendo no Mi)
What other potential logia are left? I figure, with Haki so emphasized now, we're going to get quite a few more Logia from now till the end game, so should be interesting to make some predictions based on that.
I think the names will mostly be different. While some Logia have their name directly from the substance (Croc's suna suna, CC's gasu gasu, BB's Yami Yami), most of the names come from Japanese sound/sensation words.
For instance "Hie Hie" is the feeling of "chill" (the sound that represents the feeling of being chilly). And "mera mera" is the sound of burning. Pika pika is the "sound" of sparkling.
So Aokiji, Kizaru, and Ace's fruits are based on these sound/sensation words, instead of being "koori koori", "Hikari hikari," or "honoo honoo". Another problem with the aforementioned names is that they have 3 sounds. All devil fruits 2 sounds.
ガム (gum) Luffy
ハナ (hana) Robin
ガス (gas) CC
メラ (mera) Ace
Each character represents 1 sound, so every fruit has 2 sounds. Ya-mi, Ne-Ko, Hi-To, etc. etc.
Notice that "gum gum" and "gas gas" are derived from English. While in English, we think of "gum" and "gas" as 1 syllable words, in Japanese, they're 2 sounds each (Ga-Mu), (Ga-Su). Words never end in consonants except "n" and even "n" is considered 1 sound.
Now lets take a look at the aforementioned examples:
Ice = koori = こおり
Light = hikari = ひかり
Fire = honoo = ほのお
So, if you use the name of the element, it becomes a 3 alphabet sound, which is no good. You'll notice that in the case of Ice and Fire, "oo" is considered 2 sounds, not 1 syllable like it would be in English. You really have to think about it in terms of Japanese alphabets.
Now, let's look at Aldy's examples again.
1.) Rock Rock (Iwa Iwa no Mi) イワ good, 2 alphabet
2.) Water Water (Mizu Mizu no Mi) ミズ, ok
3.) Blood Blood (Chi Chi no Mi) チ "chi" is only 1 sound, so no good
4.) Plant Plant (shokubutsu is what I'm getting but that's long lol) しょくぶつ wow, 5 sounds, obviously no go. Maybe "kusa kusa" which means weed.
5.) Air Air (Kuuki Kuuki no Mi) くうき 3 sounds, no good
6.) Wind Wind (combine 5 and 6 if too similar) (Kaze Kaze no Mi) かぜ could work.
7.) Oil Oil (Sekiyu Sekiyu no Mi) せきゆ no go
8.) Wood Wood (Moku Moku no Mi, from mokuton) もく, ok
9.) Cloud Cloud (Kumo Kumo no Mi) くも ok
10.) Metal Metal (I was getting Kane, but I thought that was more bell, so tetsu tetsu? I know that is iron or steel though) てつ sure
11.) Steam Steam (Jouki Jouki no Mi) じょうき wow, 4 sounds, no good.
12.) Clay Clay (Nendo Nendo no Mi) ねんど again, 3 sounds, no good
However, I think logia have to be somewhat non-solid, so rock and metal seem unlikely, (after all, Jozu's diamond power is not a logia) and again, up until now there have been no logia based on substances derived from living beings (or living beings), so I don't think blood, plant, or wood work.
Things like oil or clay (liquid) could be ok, but I'm not sure what names they would have. Probably have to be based on some kind of sound/sensation word though. Scarier than oil, I bet there could be a tar or acid logia. >:D
Also, because of the nature of the Devil Fruits, I kind of doubt there will ever be one that is based on liquid water. If you want a character that can abuse water, find a fishman/mermaid. >:D