Forgive me if I'm posting this in the wrong place but I have a suggestion.
I love that you can set the JPEG compression in the options but what I'm missing is a compression setting when you make the thumbnail. For example I may have an image that I have already compressed with another software and I would like to turn it off (or change the compression) for the that specific thumbnail.
So how it would work out is that in the settings you set your default jpeg compression, 70 for example, and when you thumbnail an image you see the input with the value of 70. Before you crop you can then change that compression rate or keep it the same.
Really great plugin you got here, I'll do my part to spread the word!