A long-standing feature request is for pinyin support. To date, we're here:
Based on our current roadmap, this isn't work that we will take on, as it doesn't coincide with functional areas that we plan to improve in the near future. We recognize that time and thought was put into this request, but unfortunately, we can't prioritize it at this time.
Anita Taylor, Feb 19, 2021.
As I understand, Japanese.SE utilizes this user-written script from over 10 years ago (see also GitHub and StackApps) which was updated a number of times. The impression I'm getting from Stack Exchange staff is that they're not in a position where they can adapt this script for use with Chinese.SE.
However, we may have a way forward by writing/modifying the script ourselves (or maybe even simply using unmodified Japanese.SE code), although I'm not 100% sure about what is/isn't possible. I'd like to ask...
Question: Is our userbase able to implement pinyin support?
I'm interested in finding out if writing our own script (like at Japanese.SE) is even a practical possibility. I don't have the skills for this.
When processing pinyin, there's a whole bunch of annoyances, like capital letters, spaces, umlauts with accents, Xian vs. Xi'an, and ma0 vs. ma5 vs. ma (neutral tone), varying lengths ("zhuang" vs. "e"), processing already-processed pinyin (like dàyī). Beyond pinyin, there's also the possibility of Zhuyin/bopomofo support, and support for various dialects. dROOOze lists other issues and desirable features here.
This means that support for pinyin requires familiarity with pinyin and the relevant programming skills. It's not straightforward. Thus to begin with, I suggest focusing on pinyin alone: if we list 100 different desirable features, I expect it'll indefinitely remain on the drawing board. I.e., I suggest starting small.