Hmm... that's a rather difficult challenge...are we talking dialogue-only poeming or is there narrative as well...? direct or indirect speech = active vs passive voice...how many characters' voices...and what is the POV, e.g. third person omniscient or what... yada yada.
So these questions, as you may infer, are more prose than poetry related, and tackling the task of incorporating multiple speakers into a poem is going to push things more in the direction of prose than poetry but as long as ungrammatical white space is included - (which is my baseline answer to the unanswerable question of what defines poetry) - then it's technically poetry, I guess.
But I don't know about this... perhaps if I saw an attempt, that would be indicative of a method to be refined. It's interesting because much of what is modern-form poetry includes grammatical rectitude, (except the white spaces, of course) so logically one might expect dialogue tags, even singles to keep things ' lite', but yet where narrative does occur in poetry it's almost invariably indirect speech (or at least without tags) which in turn is considered poor form in prose writing as it is passive voice. One would think that the same approach would apply to poetry writing but no, the coyness around in-your-face dialogue in poems outweighs such technique, and passive voice or more accurately on occasion, semi-passive voice, is ruling over exception.
Understand that I haven't researched or read poetry widely, so I don't have a recalled body of writing to examine for comparison or inspiration. I'm trying to think of incidences from my own writing but very little springs to mind... there was one where Yahweh and Mephistopheles were sitting on a space satellite sharing a joint while discussing the metaphysical logistics of an impending genocide, something like that, but I can't recall the form of the dialogue, most likely passive....
In fact, I can't recall ever using dialogue tags, even in other slapstick-doggerel humour attempts... if you use tags you have to go the whole hog with all related dialogue punctuation and broken and unbroken dialogue sentences, etc. Most of dialogue in modern poetry is internal or reported dialogue, and traditional soliloquy by its nature is not multi-party. So that is all a long-winded way of saying dialogue punctuation or prose-like structuring should be ruled out, for being inimical to poetry composition.
I guess the main questions are: how many speakers, and is the writing narrative only, without supporting exposition, as it were. My instinct is to say dialogue only, to keep it cleaner and tidier and formed of itself, and also to create a grammatical distance from prose; the challenge being to create and maintain something vaguely poetic within the given stricture.
So then, no dialogue punctuation worth mentioning and no supporting narrative either and at least three voices incorporating basic punctuation, commas and full stops etc, with random white space allowed to show that it should be regarded as poetry - this seems to be the departure point.
As I see it, the only options are positioning (as you mention) and varied fonts. I would say use both because you are working with minimal poetry tools to create a sustainable piece. I guess the fonts selected should try and reflect the nature of the characters, because the poem is all just about the characters expressing themselves so you want to use that, as well as to try and write the character distinctions you require into the content. I don't think I could write a successful piece under these constraints, to be frank, but let's tap something out to prove that and to see what it looks like. Scroll down,
down through the rabbit-hole's
or a philosophy from between the cabbages
I wish that wisdom had come to me
when I was a younger woman.
And then? Where would you have profited from mistakes?
If she were already wise,
there would be no need to learn from mistakes.
And all would be different. Maybe Mary would have never entered this convent
if already replete with knowledge.
Yes. And maybe this vegetable patch will weed itself with all these fine fancies flying about.
~~~~~~~~~~~~~~ ~~~~~~~~~~ ~~~~~~~~~~
~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~
Sisters, we laugh but I hazard that
I am not fated to die just yet.
Yes. And that means when you reflect upon
your yesterdays, from today onward,
from all your remaining morrows,
you will indeed be the woman
who was wise when younger.
And will that be enough to keep
any mistakes from birth?
For what is wisdom worth
without the bumps and bruises,
and the scars from which to hang
faith and love as medallions of light?
Hm. Can't say I like it much. And I don't know how I ended up in a vegetable patch at a nunnery. I also can't see it working for a large group, too much static noise. You would have to name each speaker. Fred: Don't or do not, it's all a free do-nut for me.
I basically just made it up as i went along - - - and it's cluttered and confusing, and shunting things around to create the complicated dialogue structure is a mission and not conducive to creative continuity ... but you see what I am doing, and with the speech patterns as well.
One more structural dimension that can be added for further individualism is font size. I draw the line at colouration. Perhaps grey-scale, methinks.
Some cheap alliteration and faint rhyme is thrown in as a nod to poetic elements. Italics help with the direct dialogue effect. The backslash links the speech sections in the fashion of step-down invisible but implied speech bubbles, which is sort of neat.
It's all theatrical in nature, I guess. Background exposition could be pre-built into the title, using a couple of lines in an archaic style, and making it an introductory section, like an olden days stage announcer before the curtain goes up. (Inserted something there now to demonstrate.) With the writing, it seems that longer chunks of dialogue will work better, as in the final speech 'stanza'.
On the plus side, it does seem that characters and a story can be fleshed out in this hybrid format, and readers could maybe get used to following the dialogue layout - all indicating that a long or mini-epic style format should be applied. And interesting content, of course. Eish...nuns... ha ha.
Well, that's my submission for the assignment, thanks for the challenge.
Why don't you carry on with the second half for the practice and land the exercise with a good finish? Introduce the character names too, to distinguish further and to create human engagement. Try keep the slanted shape effect going, if it works out. Aim for 4,5 or 6 line stanzas, I think. Have fun.