As an American, the width of an Australian dollar coin seems perfectly reasonable.
Coins are such a pain in the ass, but $1/2 is enough that I don't just want to refuse the change to avoid the inconveniences of carrying coins.
I have to assume that a polymer $1/2 wouldn't have this issue?
I think whether it would help is somewhat complex because polymer notes do still wear out, and lower value notes have higher usage which makes them wear out faster. IIRC the main driver for polymer was security with durability as a nice side effect.
This link https://www.rba.gov.au/publications/bulletin/2015/sep/7.html says that median life for $5 notes is 3.5 years under one measurement system, which I would presume would be even lower for $1/$2 if we used them, since they'd get more frequent usage and less storage.
It should be possible to calculate the costs, savings, and lifetime of all the coin and note variations but that's a bit much for me right now :)