I myself am a Japanese speaker and have a good command of its orthography. Katakana, like Hiragana, is a syllabary, meaning that it's not cut out for representing single consonants. Every brivla has a consonant cluster, and no Katakana except { ン } [n] can adequately represent that. Cmavo, on the other hand, have no such cluster and can at least by principle be accommodated by a syllbary. More suited for brivla -- content words -- is Kanji, the logograms. For example:
mi carna
ミ 回
ta tricu cmana
タ 木 山
Logograms, when you know them, are a great potential for speed reading.
Katakana, however, has other difficulties in substituting for ASCII. It doesn't distinguish /r/ and /l/, for instance. As you've shown above, { ri } and { li } both become { リ }. { 'a } and { xa } become { ハ }. And so on. One workaround may be to use Hiragana for one of each pair. Say, { ri | り } (Hiragana) & { li | リ } (Katakana), and { 'a | は } (Hiragana} & { xa | ハ } (Katakana}. And certain syllables would have to be represented with two letters, such as { cu | シュ }, which is a combination of { シ } and { ュ }, which is the smaller of { ユ }. It can get quite complicated for non-natives.
moklu gi'e pimlu
口 ギへ 羽
finpe vi lo rirxe midju
魚 ヴィ ろ 川 中