Actually, isn't the concept of a kana-only character system how early, domestically-marketed microcomputers in Japan did in fact work? The only example I can think of is a home entertainment console, but the Nintendo Family Computer generally used kana with a few highly common kanji.
Yes, early computers in Japan used katakana only. They were half-width (normally they are written in a square box) so as to be compatible with the Latin alphabet. This is also how telegrams were sent, starting from when Japan began modernizing in 1868.
