The unleaded petrol issue was that some older engines had soft valve seats and they used the lead in the petrol to cushion the valve on the seat. No lead meant that these engines saw accelerated valve seat wear. Owners had to fit new (harder) valve seats or find an additive that did the same job as lead but wasn't banned ("as poisonous" is a different matter...
Most additives have phosphorous in them, from memory.. which does the cushioning job almost as well as lead.
The problem with Ethanol is that it is an additional ingredient, rather than something that can be solved by an additive. You would have to take the ethanol out...
But most cars should be okay on it.. If there is 5% ethanol in the benzina already, then the seals, plastics and rubber used should be fairly or completely ethanol tolerant. If stuff fails because of the extra ethanol, then it will be a gradual failure rather than an instant one.
Replacement gaskets, tubes, seals, pipes etc. will be made out of ethanol resistant material.. so unless you have an old car and use old stock parts to replace the one(s) that have been eaten by the ethanol, you should be okay.
I'm not sure if ethanol is slightly corrosive.. as has been mentioned.. so you could have metal items being attacked by it as well as plastic. Potentially anything made of alloy could be attacked since it's softer and is made from different metals some of which could be less ethanol tolerant.
The good news is that Fiat Group have been making bi-fuel and ethanol powered vehicles for decades... and since the same parts fit on loads of different cars and are probably all made by the same few component manufacturers, the vast majority of them will be accidentally ethanol compatible anyway..