Earlier quoted context omitted.
I feel with you, but there is a nice solution :-) I moved to France from Germany, I had first to unlearn the German layout (QWERTZ) and then learn the French AZERTY. But as you say it is so bad! Additionally I was travelling for work and sometimes was exposed to type on different layouts and was very frustrated because I was accustomed to AZERTY. After one week in Russia I took the decision and switched to QWERTY, co…
I think you can never get the Turkish "ı" and "İ" with any sane combination on any other keyboard than the Turkish though. I'm Turkish and have been living in Germany since more than 5 years and I still use a Turkish Q layout just for this reason (I occasionally have to write in Turkish). It also contains all the German letters under relatively sane combinations.
AltGr . + i => ı AltGr . + I => İ
I think this is what you were looking for and I find this combination easy to remember and other combinations seem to follow mostly the same principle (e.g. " (double quotes) modifies the double dots on the letters, which allows to make öÖäÄüÜëË, etc. The same for ~ (tilde), ` (backtick), ' (single quote).
Here the combination for the special Turkish characters:
Ç -> AltGr + % + C or AltGr , (comma) + C
ç -> AltGr + % + c or AltGr , (comma) + c
I remember this combination because the on the % key there is 5, or to say it differently % = Shift + 5, and 5 resembles a bit the symbol that goes below the C in Ç. The same is true for Şş
Ğ -> AltGr + Shift + 9 + G
ğ -> AltGr + Shift + 9 + g
I remember these because (Shift + 9 corresponds to '(', i.e. opening bracket, which truned by 90°to left is like the sign that is on top of ğ and Ğ
ı -> AltGr + . + i
İ -> AltGr + . + I
Ö -> AltGr + " + O
ö -> AltGr + " + o
Same principle for üÜ (and äÄ if you need German as well)
Ş -> AltGR + % + S
ş -> AltGr + % + s
Ü -> AltGr + " + U
ü -> AltGr + " + u