At the moment we plan to use the MoE systems internally - Tai-Lo and Taiwanese Hakka - essentially because they're the ones with the greatest level of standardization, which is kind of important when you're building an app around them. However we can certainly add other systems just as we do with Mandarin, in fact we've made this a whole lot easier and more standardized internally (which is why we can offer Wade-Giles and GR).