Here are two extracts from Bavinck on objections to penal substitution:
...Satisfaction is not necessary. God's righteousness and mercy are not opposed to each other, and these attributes are not characteristic of God's nature but the effects of his will and dependent on his will. Whether or not God wants to punish or forgive sins is determined not in any way by his nature but his will. God can just as well--and better than a human being--forgive sins without satisfaction. In fact, his justice is nullified by satisfaction, because it punishes the innocent and acquits the guilty; and his mercy loses its value if it can only manifest itself after satisfaction. God, accordingly, has always promised forgiveness to the penitent and wants us to follow him in that respect.
...the doctrine of satisfaction is also harmful because it elevates Christ with his mercy above God with his demand for satisfaction. It obligates us to be more grateful to Christ than to God...
Herman Bavinck, Reformed Dogmatics: Sin and Salvation in Christ, p. 348-9
Now the question I have is whether these objections are more likely to find a hearing, or sympathy, in mainstream evangelicalism or whether they would be exposed and refuted. What do you think?