Hi there, i'm actually very interested to hear you pov, perhaps you could share. I was at two minds on deciding between both sublegends and decided to post one option for IC feedback ^^.
While both zhuyin and cangjie are used for inputting Chinese characters, zhuyin is primarily used in Taiwan. But pandas are not originated from Taiwan.
Pandas are from mainland China (specifically, Sichuan province), where pinyin is the most popular Chinese inputting system, followed by wubi. Cangjie is very niche and considered "hard to use" for the purpose of entering Chinese.
Personally, if I have to pick between the two, cangjie sublegend at least are made of Chinese characters which feels closer than zhuyin (which are closer to symbols than actual Chinese characters).
Alternatively, if the desire is to go with non-sense alphas -- as I don't think those who buy the cangjie legends will actually try to look at the keyboard when they type -- then you could go with the character "竹" (which means "bamboo") for all alpha keys -- this will also match your all bamboo novelties.