The pronunciation of words spelled with "-ti-" in German seems to be a little complicated. I read in a book that "-ti-" is pronounced as "-zi-" (I believe only when a vowel follows) in words like Aktie or Patient, but that words from French such as Aristocratie may have stressed /tiː/ instead.

It seems to me that it would be simpler to just use spellings like Akzie and Pazient instead. That kind of use of Z has precedent in some other languages, such as Italian ("paziente"). I know that "ce" and "ci" in Latin-based words are often replaced with "ze" and "zi" respectively in German, and I am wondering why the use of the letter Z did not also become usual to represent the same sound in words that have "ti" in Latin. I wonder whether the spelling "ti" has been kept out of some concern that using "zi" would obscure the etymological distinction between words that had -ci- and -ti- in Latin. Did any scholars or spelling reformers ever comment on this topic?