Have you tried each available Chinese-capable keyboard with each available Chinese language pack? (I don't know any written Chinese in either style, but I do know that there are two styles, so that complicates things even more.)
As for a Chinese-reading developer willing to spend the time with you to understand exactly what you want, then the time to develop, test and debug the app (nothing in app development is simple - there are always bugs), for nothing but giving you an app you want, the chance is pretty slim, unless he or she has already developed one because he or she feels the same as you do and is capable of doing something about it. (That's how a lot of free apps originate - the developer needs an app to do something, develops the app, then releases it for free because ... why not? [I just wrote a little routine to generate any number of Fibonacci numbers, but that's too trivial to turn into an app - but I've released things I've developed that I thought might interest others (and one got joke-renamed by a PC World editor).])