And i would have to argue your use of the word "Umlaut". It´s a good word, but you english speakers would probably would have been better off inviting a new word, Umlaut was invented for certain mutations in vowels in germanic languages:
a-Umlaut, i-Umlaut und u-Umlaut, and it´s used for ä, ö, ü, äu.
(btw, if you believe ä would be an a-Umlaut, you are wrong, it´s an i-Umlaut^^)
The way you used it wasn´t the original way, so i strongly suggest you find a new word for this new stuff. ï doesn´t exist in Umlaut definition, if you want to increase the range here, you better chose a neologism, not everything with 2 dots is an Umlaut^^ No problem if you want to steal our words, we do the same all the time, but don´t change the sense if you do so (and don´t tell me if we do it, i really hate that too)
Overall grade, B+. Shows promise, vocabulary strong but uneven, worthy of language history training and needs some more creativity.