The nice thing about zkrollups is that users have a cryptographic guarantee of being able to withdraw their money. The rolled-up transactions are posted on chain in compressed form, and a contract on chain verifies a concise proof that all the rules were followed, including that all transactions had valid signatures.
So if this is done correctly, any master keys shouldn't be able to steal user funds. The key holders would be the ones authorized to post the data, but the worst they could do is censor transactions.
So if this is done correctly, any master keys shouldn't be able to steal user funds. The key holders would be the ones authorized to post the data, but the worst they could do is censor transactions.