I believe the cross-linked html ToC is indeed the way to go, it's what I prefer for collections of this kind.
I don't read much verse, so don't have much opinion. Suggesting to read a poem in Landscape mode doesn't seem like an outrageous demand. Some readers probably would always stay in portrait mode anyway and suffer with less-attractive line breaks. Anyway, the poets can't enforce such wishes unless they send Landscape-police to tail every reader to check up on them. Bullhorn announcement: "Ma'am, you MUST swivel your reader to landscape-mode, or we will issue a ticket!"
Or you could transform the text to run vertically on the page, and force the reader to swivel the screen (that would be evil!)