While, phonetically, there are other letters that make the same sounds, that
only works if you ignore pronunciation rules.
The difference between “c” and “k/s” often indicates the way the preceding or following vowels are to be pronounced, and which of the possible pronunciation of the letters to use. (for example, s can be pronounced multiple ways).
For example “rice” re-spelled following your rules would be “rise”, which can be confused with the word “rise”. A common solution posed for that is to re-spell “rise” as “rize”, but that spelling changes how the e or the i is pronounced. Sure, hypothetically, one could re-structure how the vowels are used, but every time we kick the can like this, hundreds or thousands more words have to be re-spelled, and it rapidly becomes unusable.
We
could get rid of c by just brute force, but you end up just adding ambiguity, or having to change the spelling of most words, neither of which make a helpful spelling reform.