You find on this page decisions made by the orthography committee so far.
/c/ is not a consonant sound in the language. The letter c only occurs in the digraph ch. It stands for /ʧ/ which was used at certain times. The use of /ch/ was a matter of convenience. It as well is similar to the usage in English.
In languages like Nchumburung, Kaakye (Krachi), Nkonya /ky/ is used instead of /ch/. This is because they adapt to the Ashante Twi usage. It was decided to maintain the use of /ch/ though there is no /c/. This is what UEW and BATCO are teaching.
There was a comprehensive discussion about the use of the additional vowels /ɪ / and /υ/.
The committee agreed to maintain the use of the seven vowel for writing. However we should not forget that /ɪ / and /υ/ are used when transcribing words.
The alphabet as described here was reviewed and accepted.