Thank you all for replaying and your tips!
only thing I would suggest you is to group the F-keys in 4-key arrays for touch typing (reducing backspace/esc size)
That's something I considered; reducing the esc key seems to be no problem, but the backspace key would be to small and would need a relocation (With a different enter shape it might work to set both backspace and the del key one row down)
1) Keyboards as they are nowadays been already right-hand-heavy. If you're adding a full column of alpha keys with symbols, have you considered doing it the left of the 1QAZ column?
I didn't think about this, but it's not a full column, not for the iso standard, I moved one key from left to right and add one where the backspace key should be. But I will think about it, although I'm pretty used to use my right hand for all kind of special characters (maybe not the best way to type ^^ I really move my arm to the right if I use these keys. Is this bad in general?)
2) Mods should be presents on both sides. I don't see RALT (a.k.a. AltGr) there.
AltGr isn't needed in this layout and I want to avoid it for more simplicity. Also Alt is generally not a often used key (starting a command/program/whatever mostly used one at a time = not a normal flow writer-user case, programmer-user maybe but more or less to start single commands or tools, gamer-user use them differently)
In the Japanese layout it would make sense because of the possibility to use latin characters quickly but also you should think if this user case make sense at all (would one key for right-handed people be enough)?
3) Mode selectors (as opposed to mods) seem to be plentiful. Have you considered having status lights to tell you on what mode you are at any given moment?
The Japanese layout uses indeed a led indicator to show if you are in the Hiragana, katakana or latin mode (toogle quick between Hiragana and Katakana with the dedicated key right of the space bar (the reuse/absents of the caps-key makes it irrelevant to use a caps-lock indicator.
Maybe I should say that:
13
24
1 = Hiragana, 2 = Katakana, 3 = latin, 4 = special
4) Using mod-chords to access the F row strikes me as a bad idea. How will you, for example, press Ctrl-F5 instead of F5? The keyboard is already six row talls as it stands... why not move the F row to two left-side columns, XT-style?
I would use two fingers or do you mean something else? The F5 function would be operated like normal if you press Crtl F5 or in latin mode with just F5 (latin mode would one be used if writing kanji with the IME or if someone would actually write in Hepburn on the internet ^^)
Yes 6 rows are a lot! The only option would be to remove all Katakana labeling (assume everyone knows the right equivalent of the corresponding Hiragana and move all special characters down, what maybe could look even more confusing as it is
The good thing is only that it would be "easy" to write on 4 rows if you get used to it, my fingers can reach quite comfortably the number row (but this row is middle and ring finger only)
The xt-sytle looks very nice! (But only F1-10 on 5 row keyboards? Bios uses F11 and F12. So they would need a new location) I think I will use this in my German Layout.
5) The backspace key seems to be too far away (also, I dig the enlarged Del key).
Hmm you are right, maybe I should swap backspace and delete, but this would mean a smaller backspace key
["dig" is good is it? Thank you I like it this way too, the delete key is a very usefull function]
6) The Enter key with that exact size and shape will be a pain to obtain. Go BAE (and adjust the width of the neighboring keys) or go small-ANSI (and gain the space for one more key).
then I will go BAE. But is there no manufacturer that has all keys in all shapes? To many dreams? Okay what about 3D printed are there any good?
7) Which of all the keys is the Fn key?
There is no Fn key like on multi function keyboards or laptops. I meant F1-12 sorry!
8) Swap the euro and pound signs; the way things are going, we'll be using the former way more than the latter quite soon.
9) I dig that you're also using the dotted circle as a stand-in for the "any letter" when dealing with common diacritics.

Haha I didn't intend to be Political but let see how thinks are going ^^ But the pound sign is anyway on second place on this Key
Thank you, It's just easier to understand, No joke I didn't know this until I was 20...
Do you really need a Caps-Lock key? I have never used that key in my life, it must be from the era of typewriters. The only time I hit that key was no accident...
That's the reason I replaced it in the Japanese layout. ^^ I should consider a remove of this key, because your are right, the caps-lock is a rarely used key (In my user-case anyway I didn't write long sentences in capital letters)
The layout is missing PgUp and PgDown keys. I use those often.
Correct me if I am wrong, but aren't these keys just for scrolling? I think I would use my mouse in these cases.
I you are going full custom and you touch-type then why not something more ergonomic (split and column staggered). E.g. something like Ergodox?
Oh no I don't like these ergonomic keyboards, they are to weird for me, especially a split keyboard
Thank you again! I will make a 2.0 version of both Layouts