Can "wouldn't" be reduced to the clitic -'dn't when attached to any other pronoun besides y'all, such as she'dn't or you'dn't?
(Appearing for example in "y'all'dn't've" from formal English "you all would not have")
To address the primary question, you can use more than "y'all" with the following contraction of "would not have", for example "I'dn't've".
Actually, I would not normally contract "y'all" along with the following. I'd more likely say "Y'all wudn'tve", or even "Y'all'd" for 'you all would ...".
For clarification, there's no standard way to write whatever you're trying to say as a contraction because contractions beyond two words are not really standardized in formal writing by style guides, though popular informal instances may try to write out longer sequences of contractions similarly according to general English spelling principles like "shouldna" or "shouldn't've" for "should not have". So any question should expect leeway in writing. Frankly also leeway in pronunciation because the phonology is a bit fuzzy in natural informal sped-up speech.
Never heard/seen it used in that form. 'Round here (eastern NC), it's I/you/y'all wouldn't've/couldn't've/shouldn't've, &c.