How good are Chinese characters for writing English?
Provided you have prior knowledge of what is considered Standard Chinese at any point in time, whether it be Mandarin now or the various forms of Classical Chinese at earlier points in time, . . .
Otherwise, they're really not that great for writing English. They only barely fit written Japanese and written Korean because the written language was modified to suit the characters. Having said that, considering that Chinese characters at one point formed a syllabary in ancient times which broke down over time, based on prior knowledge of Sanskrit one would need to do a phonological analysis of English at the time (making it easier to devise
fanqie to suit English pronunciation of Literary Chinese), then standardize the phonetic parts of Chinese characters to provide a consistent reading (even if it requires more syllables than the Chinese original). The semantic part of the Chinese characters would be ignored in this case - as, in fact, most Chinese are wont to do.
This is when it gets interesting, because most non-Chinese readings of Literary Chinese are based on
Middle Chinese, whose contemporary analogue at this point in time is, in fact, the common ancestor of both Anglic languages (English and Scots) and
Frisian. That's if the adoption of characters happens around this same time, so even here the "fit" between grapheme and phoneme would break down as language naturally changes. So there would be as much difficulty learning Standard Written English with characters as there is Modern Written Chinese with Standard Mandarin pronunciation and characters (if you're not using bopomofo or Pinyin first).