I encourage you to read Unified Addresses Composition - #45 by nuttycom to understand why we have not yet implemented transparent address rotation. The TLDR summary (even though you should read that whole post) is that at present, there is no way to implement a wallet receiving funds at multiple different transparent addresses while maintaining the unlinkability of those addresses from the perspective of a lightwalletd-compromising adversary. At least, there’s no way to implement it in a privacy-preserving fashion that doesn’t have significant usability downsides (think on the order of it taking half a day to detect received transparent funds.)
Rather than implement something insecure (as other wallets have chosen to do) we have opted not to implement transparent address rotation. At least with the current behavior of Zashi, the user knows that they’re linking their behavior if they reuse a transparent address. We won’t implement a feature that gives users a false sense of security.
We know how to implement the feature that is needed, but this requires a change to the light wallet protocol and for those changes to be propagated throughout the ecosystem. That’s work that’s currently in progress.