You are entirely right. Perhaps you have read What is Faith? by J. Gresham Machen. I was looking for my copy just now, but to my irritation it seems to have disappeared. Perhaps I lent it to someone and he hasn't returned it.Faith alone just means that it is the one thing in our justification that we are actually involved in. It's the means whereby be are united with Christ. If you take on justification by faith alone you are not just taking on Austin but Jonathan Edwards and all the reformers. As far as merits for our justification the shed blood of Christ is the merit. If you look at faith as one of the things we bring for justification in the sense of a quality or merit then the OP is right in that it has become a work.
In the book, Machen likens faith to an electric cable; it is that which connects us to the power of God. You say, surely that is the Holy Sprit? Indeed. It is the Spirit who gives us faith to seek and find God.