Here are a few characters taken from http://en.wikipedia.org/wiki/Bopomofo that I'd like to see added to the database, so I can properly complete my list of characters used in the making of zhuyin (this isn't about adding zhuyin to skritter, just the origin characters).

冂, the archaic character and current radical 冖 mì

𠄎, ancient form of 乃 nǎi

ㄑ quǎn, graphic root of the character 巛 chuān

厂 han3 "cliff" radical in Chinese characters (Kangxi radical 27)

𠀀 hā, inhalation

𠀅 hài, bronze form of 亥

ㄢ hàn "to bloom", preserved as a phonetic in the compound 犯 fàn

乚 yǐn

厶, an obsolete form of 厷 gōng

Oh and just want to say that I'm pleased to see that a lot of the "archaic" and "obsolete" characters that go behind zhuyin are already on here, that's great! Nice to see characters that wont be used for much else other than historical purposes.

List is here http://www.skritter.cn/vocab/list?list=161348327

厂 we have, but that's not han3--it's chang3.
冂 we have listed as jiong1.
厶 is in as si1.
乚 we have.

ㄑ and ㄢ are not in the proper range for a CJK character, so we'd have to make some changes to get them in. I don't think it is a high priority, though.

The others are outside the Basic Multilingual Plane--our tools don't support the Unicode codepoints they needed.