The function of pinyin should be able to be implemented with this
https://github.com/Towdium/PinIn

Will REI's Pinyin search conflict with JustEnoughCharacters' Pinyin support for REI. Maybe we should remove REI support from JustEnoughCharacters in the future?

There will be an api to add custom input methods, but rei will come with its own as well, if there are any ime rei itself doesn't support (i.e. I don't support duopin), JEC can support that

Added the feature, the docs can be found here,