Stokoe and HamNoSys are very easy to write using computers, and can use fonts and normal text rather than special markup languages. (clustering "sig" characters in Stokoe present a difficulty, but not an impossibility, for the average font-founder)
Why not write in any of those, and generate any of the SignWriting ones? Or user's choice and conversion, like Simplified/Traditional Chinese? Anyway, using written English is probably the worst option.