I just had another idea about steg poems. You could also use a binary scheme. Unfortunately it’s even less practical, as you need even more lines for each letter. My previous scheme involved a 26 line key, then one line per letter. So for a message X letters long, it would take X+26 sentences.
Unfortunately to translate a single letter to binary requires eight sentences. So while it took 22 sentences to hide “help me”(32 if we had written out the full key), it would take 48 sentences if we used binary.
And I don’t think I could write a 48 line poem with only two rhyme sounds.