Also considering structural attributes for the standoff so as to mark lyric stanzas, episodes etc. Some ideas (these would be applied to each syllable in a section, but would refer to the entire section; I know this could be done with enclosing tags, but for the sake of simplicity and flexibility the verse xml is intended to be equivalent to csv):

div="prologue" style="ia"
div="episode" style="an"
div="episode" style="ia"
div="episode" style="tr"
div="choral" style="de" stanza="strophe"
div="choral" style="de" stanza="antistrophe"
div="choral" style="ae" stanza="epode"
div="choral" style="do" stanza="epode"
div="kommos" style="do" stanza="strophe"
div="choral" style="io" stanza="strophe"

Are there other formal sections that deserve marking? Agon? Epirrheme/Syzygy? I guess I can deal with these as I come to them (esp. when I get to comedy), but it would be nice to have a clear view of the ontology early on. The trick is to distinguish between form and content (e.g. what makes an agon an agon?).
There are 4 top level categories here: prologue, episode, choral, kommos. I am tempted to see prologue as a type of episode, and kommos as a type of choral, but for now they seem legitimately distinct. I don’t currently plan to mark parodos and exodos, since these are always choral[0] and choral[-1] (right?). Well, I know there is in fact a variety of ways a chorus is introduced to an audience (or says goodbye to it) – frogs and furies come to mind – but that seems like a good reason not to overprivilege the parodos/exodos category.
Also these are the ‘features’ a syllable can have. Colon and period mark the final syllable in lyric units, though colon is arguably equivalent to line, and so might not be used. lbn = long by nature – marks long αιυ where accent or iota subscript don’t do this. bil = brevis in longo. empty is for added syllables without a conjecture about content. link is for DE link sylls.

'diastole', 'systole', 'res1', 'res2', 'lbn', 'hiatus', 
'bil', 'synizesis', 'crasis', 'elision', 'empty', 
'anceps', 'added', 'link', 'colon', 'period'