Instead, I would use a recursive function which, given a string s an index n, and a dictionary d of characters in collating-sequence, would seek to “increment” the character at position n. This function, if given an index n that is less than the leftmost position of s, would simply return s. If it found that it had “wrapped-around” the character at position n, would recursively call itself with n = n-1. I would write such a routine to be “Unicode aware,” and I would have confidence that it actually worked.

Go on then, do it. Show us. Any language you like. Show us.